Download - Chemistry Book One
Chemistry
2014
FOR CLASS IX
SIR. MOHAMMAD AHTISHAM ALI
ABDULLAH EDUCATIONAL SOCIETY http://facebook.com/aes.pk
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Contents
Q - 1) DEFINE CHEMISTRY? WRITE THE NAME OF ITS BRANCHES: 6
Q - 2) WHAT IS SCIENTIFIC METHOD? DEFINE HYPOTHESIS AND THEORY. 6
Q - 3) WHAT IS SCIENTIFIC METHOD? WRITE NAME OF ITS FOUR STAGES AND DESCRIBE THEM: 7
Q - 4) WRITE DOWN THE CONTRIBUTION OF MUSLIM SCIENTISTS IN THE FIELD OF CHEMISTRY: 7
Q - 5) WHAT IS SCIENTIFIC LAW? 7
Q - 6) WRITE DOWN THE CONTRIBUTIONS OF MODERN SCIENTISTS IN THE FIELD OF CHEMISTRY: 8
Q - 7) WHAT IMPORTANT ROLE CHEMISTRY PLAYS IN THE SOCIETY: 8
Q - 8) WRITE THREE SIGNIFICANT REASONS TO STUDY CHEMISTRY? 8
Q - 1) SATE THE FOLLOWING LAWS: 9
Q - 2) STATE LAW OF CONSERVATION OF MASS WITH LANDOLT’S EXPERIMENTS: 9
Q - 3) STATE THE LAW OF CONSTANT PROPORTION WITH EXAMPLE? 9
Q - 4) STATE THE LAW OF MULTIPLE PROPORTIONS WITH EXAMPLE: 10
Q - 5) STATE THE LAW OF RECIPROCAL PROPORTION WITH EXAMPLE? 10
Q - 6) WHAT IS EINSTEIN THEORY? & WRITE REACTION B/W MASS & ENERGY: 10
Q - 7) WHAT IS CHEMICAL REACTION? DEFINE AND GIVE EXAMPLE EACH OF THE FOLLOWING: 10
Q - 8) WHAT IS CHEMICAL REACTION? DEFINE & GIVE ONE EXAMPLE EACH: 11
Q - 9) WHAT IS CHEMICAL REACTION? DEFINE & GIVE ONE EXAMPLE OF EACH: 11
Q - 10) WHAT IS EMPIRICAL FORMULA? GIVE AN EXAMPLE: 12
Q - 11) WHAT IS MOLECULAR FORMULA? GIVE AN EXAMPLE: 12
Q - 12) DEFINE THE FOLLOWING: 12
Q - 13) CAN ONE SUBSTANCE HAVE THE SAME EMPIRICAL FORMULA AND MOLECULAR FORMULA? EXPLAIN
WITH EXAMPLES: 12
Q - 14) WHAT IS CHEMICAL EQUATION? WHAT IS A CO-EFFICIENT AND EXPRESSION? GIVE AN EXAMPLE OF
BALANCE EQUATION: 13
Q - 15) THE VALUE OF CARBON IN PERIODIC TABLE IS 12.011 A.M.U RATHER THAN 12.00 A.M.U. EXPLAIN
IT: 13
Q - 16) DIFFERENTIATE EMPIRICAL FORMULA AND MOLECULAR FORMULA: 13
1. PHYSICAL CHEMISTRY 6 2. ORGANIC CHEMISTRY 6 3. INORGANIC CHEMISTRY 6
4. BIO CHEMISTRY 6 5. ANALYTICAL CHEMISTRY 6 6. INDUSTRIAL OR APPLIES CHEMISTRY 6
7. NUCLEAR CHEMISTRY 6 8. POLYMERIC CHEMISTRY 6 9. ENVIRONMENTAL CHEMISTRY 6
(i) LAW OF CONSERVATION OF MASS: 9 (ii) LAW OF DEFINITE PROPORTIONS: 9
(iii) LAW OF MULTIPLE PROPORTIONS: 9 (iv) LAW OF RECIPROCAL PROPORTIONS: 9
(I) ATOMIC MASS ..................................... 12 (II) MOLE ............................................ 12
(III) MOLAR MASS ..................................... 12 (IV) AVOGADRO’S NUMBER ........................... 12
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Q - 1) WRITE DOWN THE MAIN POSTULATES OF DOLTON ATOMIC THEORY: 14 Q - 2) DESCRIBE MODERN ATOMIC THEORY: 14 Q - 3) WRITE DOWN THE PROPERTIES OF CATHODE RAYS? 14 Q - 4) WRITE DOWN THE PROPERTIES OF POSITIVE RAYS? 14 Q - 5) DESCRIBE THE DISCOVERY OF ELECTRONS (CATHODE RAYS) 15 Q - 6) DESCRIBE THE DISCOVERY OF PROTONS: (POSITIVE RAYS) WHAT ARE PROTONS AND HOW WERE THESE PRODUCED?
15 Q - 7) DESCRIBE THE DISCOVERY OF NEUTRONS: 16 Q - 8) DESCRIBES THE PROPERTIES OF ELECTRON, PROTON AND NEUTRON: 16 Q - 9) WHAT ARE THE NAMES OF SUB – ATOMIC PARTICLES? WHAT ARE THE MASSES IN ATOMIC MASS UNITS (A.M.U) AND
WHAT IS UNIT CHARGES EACH? 16 Q - 10) DEFINE (I) ISOTOPES (II) MASS NUMBER (III) ATOMIC NUMBER 16 Q - 11) WHAT IS MEANT BY RADIOACTIVITY? DRAW A LABELLED DIAGRAM SHOWING THE SEPARATION OF ALPHA, BETA AND
GAMMA RAYS: AND ALSO WRITE THE PROPERTIES OF EACH: 17 Q - 12) DESCRIBE THE RUTHERFORD’S EXPERIMENT, WHICH LED HIM TO THE DISCOVERY OF THE NUCLEUS OF AN ATOM? OR
DESCRIBES RUTHERFORD’S EXPERIMENT OF GOLD METAL FOIL: 18 Q - 13) EXPLAIN NEIL BOHR’S ATOMIC THEORY: 19 Q - 14) WRITE DOWN THE APPLICATION OF ISOTOPES: 19 Q - 15) C – 14 AND N – 14 BOTH HAVE SAME MASS NUMBER YET THEY ARE DIFFERENT ELEMENTS, EXPLAIN: 19 Q - 16) IN WHAT WAY ISOTOPES OF A GIVEN ELEMENT DIFFER FROM EACH OTHER. 19 Q - 17) WHAT ARE ISOTOPES? WRITE THE SYMBOL OF PROTIUM, DEUTERIUM AND TRITIUM WITH THEIR ATOMIC NUMBERS
AND MASS NUMBERS. 19
Q - 1) DEFINE THE FOLLOWING: 20
(I) DOBERNEIR’S RULE OF TRAID 20 (II) MODERN PERIODIC LAW 20 (III) ELECTRONEGATIVITY 20
(IV) PERIODICITY 20 (V) ATOMIC RADII 20 (VI) IONIZATION ENERGY 20 (VII) PERIOD 20 (VIII) ELECTRON AFFINITY 20 (IX) GROUP 20
Q - 2) WRITE CHARACTERISTICS METALS, NON – METALS AND METALLOIDS: 21 Q - 3) DESCRIBE PROPERTIES OF TRANSITION ELEMENTS: (GROUP IB TO VIIB) 21 Q - 4) DESCRIBE THE PROPERTIES OF GROUP I A, TO GROUP VIII A: 21 Q - 5) IF AN ELEMENT CONTAINS TWO SHELLS ONLY AND ITS OUTER MOST SHELL CONTAINS FIVE ELECTRONS THEN TO WHICH
GROUP THE ELEMENT BELONGS IN THE PERIODIC TABLE. NAME THE ELEMENT. PREDICT ITS PERIOD. 23 Q - 6) WHAT DO YOU MEAN BY LONG FORM OF PERIODIC TABLE? EXPLAIN SOME OF ITS APPLICATION: 23 Q - 7) DISCUSS SOME OF THE PHYSICAL PROPERTIES OF THE ELEMENTS WHICH EXHIBIT PERIODICITY. 24 Q - 8) HOW DOES THE MODERN PERIODIC LAW DIFFER FROM MENDELEEV’S PERIODIC LAW? EXPLAIN GROUPS AND PERIODS
IN MODERN PERIODIC TABLE: 24 Q - 9) WHAT DO YOU UNDERSTAND BY PERIODIC CLASSIFICATION OF ELEMENTS? WHAT ARE THE MERITS AND DEMERITS OF
CLASSIFICATION OF ELEMENTS: 24 Q - 10) WHAT DO YOU UNDERSTAND BY REPRESENTATIVE AND TRANSITION ELEMENTS? OR WHAT DO MEAN BY TRANSITION
ELEMENTS? WRITE THE GENERAL PROPERTIES/CHARACTERISTICS OF TRANSITION ELEMENTS. 25 Q - 11) WHAT ARE LANTHANIDES AND ACTINIDES? ARE THEY D OR F – BLOCK ELEMENTS: 25 Q - 12) STATE MENDELEEV’S PERIODIC LAW. DESCRIBE MENDELEEV’S PERIODIC TABLE AND ALSO WRITE DOWN THE MERITS
AND DEMERIT OF MENDELEEV’S PERIODIC TABLE: 25
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Q - 13) EXPLAIN NEWLAND’S LAW OF OCTAVE. HOW THIS LAW PROVIDE THE LARGER SCOPE FOR THE CLASSIFICATION OF THE
ELEMENTS: 26
Q - 1) DEFINE CHEMICAL BONDING AND DISCUSS HOW ATOMS UNITE AND CHANGE INTO MOLECULES: 27
Q - 2) WHAT ARE THE MAIN TYPES OF BOND? DESCRIBE THEM: 27
Q - 3) DEFINE: (I) SINGLE COVALENT BOND (II) DOUBLE COVALENT BOND AND (III) TRIPLE COVALENT BOND? OR WHAT ARE
THE TYPES OF CHEMICAL BONDING? 28 Q - 4) WHAT HAPPENS TO ELECTRONS, WHEN ELEMENTS COMBINE? 28
Q - 5) WHAT PART OF THE ATOM IS INVOLVED IN THE FORMATION OF CHEMICAL BOND? 28
Q - 6) EXPLAIN WITH EXAMPLES? HOW ELEMENTS ARE UNITED BY ELECTROVALENT BOND? 28
Q - 7) WHAT COMMON PROPERTIES ARE SHOWN BY IONIC COMPOUND? 29
Q - 8) WHAT IS MEANT BY COVALENT BOND? WRITE ELECTRONIC FORMULAS OF ANY COVALENT MOLECULES? 29
Q - 9) ACCOUNT FOR THE FACT THAT SOME COVALENT BONDS ARE POLAR AND WHILE OTHER IS NON – POLAR? 30
Q - 10) WHAT IS CO – ORDINATE COVALENT BOND? EXPLAIN WITH EXAMPLES: 30
Q - 11) DEFINE THE TERM COVALENT BOND? HOW DOES A COVALENT BOND DIFFER FROM CO – ORDINATE COVALENT BOND?
31 Q - 12) EXPLAIN ELECTRONEGATIVITY WITH THE HELP OF LINUS PAULING TABLE: 31
Q - 13) GIVE CHARACTERISTICS OF COVALENT COMPOUNDS: 32
Q - 14) WHAT IS CHEMICAL BOND? DEFINE IONIC BOND. EXPLAIN THE MECHANISM OF THE IONIC BOND IN NACL (SODIUM
CHLORIDE)? 32 Q - 15) WHAT IS COORDINATE COVALENT BOND? HOW A COORDINATE COVALENT BOND IS FORMED BETWEEN AMMONIA
(NH3) AND HYDROGEN ION (H+) PRODUCING AMMONIUM (NH4+) RADICAL. EXPLAIN. 33
Q - 16) DEFINE TERM METAL AND DESCRIBE METALLIC BOND? 33
Q - 17) EXPLAIN THE FOLLOWING PROPERTIES OF METALS: 33
Q - 18) WHY SOME METALS SUCH AS SODIUM OR POTASSIUM IS SOFT WHILE OTHER ARE HARD? EXPLAIN: 33
Q - 19) EXPLAIN THE ORIGIN OF DIPOLE – DIPOLE FORCES BETWEEN THE MOLECULES, AND GIVE EXAMPLE: 34
Q - 20) WHAT DO YOU MEAN BY DISPERSION FORCES WHY ARE THEY ALSO CALLED LONDON FORCES? 34
Q - 21) WHAT IS HYDROGEN BONDING? WHAT TYPE OF FORCES, EITHER INTRA – MOLECULAR OR INTER MOLECULAR FORCES
ARE PRESENT IN HYDROGEN BONDING? 34 Q - 22) WHAT DO YOU MEAN BY INTRA – MOLECULAR AND INTER MOLECULAR FORCES (VANDER WAALS’S FORCES)?
34
Q - 1) DEFINE THE FOLLOWING TERM: 35
Q - 2) DEFINE KINETIC MOLECULAR THEORY AND ITS STATES OF MATTER: 35
Q - 3) HOW IS SOLID CONVERTED INTO LIQUID? EXPLAIN IT: 36
Q - 4) WHAT DO MEAN BY LIQUID? DESCRIBE INTERCHANGE OF LIQUID TO GAS: 36
(I) SOLID .................................................. 35
(II) FUSION ................................................. 35
(IV) SUBLIMATION ........................................... 35
(V) BOILING POINT ......................................... 35
(VII) DIFFUSION ........................................... 35
(VIII) BROWNIAN MOVEMENT .............................. 35
(III) EVAPORATION ....................................... 35
(VI) MELTING POINT ...................................... 35
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Q - 5) WHAT IS DIFFUSION? EXPLAIN ON THE BASIS OF KINETIC MOLECULAR THEORY: 36
Q - 6) WHAT ID BROWNIAN MOVEMENT? EXPLAIN WITH EXAMPLE: 36
Q - 1) DEFINE THE FOLLOWING TERM: 37
Q - 2) DEFINE SOLUBILITY AND DISCUSS THE FACTORS AFFECTING SOLUBILITY: 38
Q - 3) DEFINE INSOLUBLE IMPURITY AND SOLUBLE IMPURITY: 38
Q - 4) DEFINE SATURATED, UNSATURATED AND SUPER STURATED SOLUTION: 39
Q - 5) WRITE DIFFERENCES BETWEEN SOLUTION AND SUSPENSSION: 39
Q - 6) NAME THE SOLUTE AND SOLVENT IN THE FOLLOWING SOLUTION: 40
Q - 7) EXPLAIN WHY: 40
Q - 8) WHAT DO YOU MEAN BY PERCENTAGE CONCENTRATIO, SOME EXAMPLE OF SUSPENSSION IN DAILY LIFE. 41
Q - 1) DEFINE THE FOLLOWING TERM: 42
(I) ELECTROCHEMISTRY 42 (II) ELECTROLYTES 42
(III) NON – ELECTROLYTES 42 (IV) ELECTROLYSIS 42
(V) ELECTROPLATING 42 (VI) ELECTROCHEMICAL EQUIVALENT 42
(VII) AMPERE 42 (VIII) COULOMB 42
(IX) FARADAY42 (X) BATTERIES 42
Q - 2) STATE AND EXPLAIN FARADAYS FIRST LAW OF ELECTROLYSIS: 43
Q - 3) STATE AND EXPLAIN FARADAYS SECOND LAW OF ELECTROLYSIS: 43
Q - 4) WRITE DOWN THE RELATIONSHIP BETWEEN EQUIVALENT MASS AND ELECTROCHEMICAL EQUIVALENT: 43
Q - 5) WHAT DO MEAN BY PRIMARY CELL ALSO DESCRIBES CONSTRUCTION AND WORKING OF DRY CELL WITH DIAGRAM:
44
Q - 6) DESCRIBES THE CONSTRUCTION AND WORKING OF DANIEL CELL WITH DIAGRAM: 44
Q - 7) WHAT HAPPENS WHEN ELECTRIC CURRENT IS PASSED THROUGH ACIDULATED WATER? GIVE THE REACTION AT TWO
ELECTRODES AND MENTION THE PRODUCTS AT CATHODE AND ANODE. 46
Q - 8) PREDICT THE NET ELECTROLYSIS REACTION WHEN MOLTEN NACL IS ELECTROLYZED. OR DESCRIBE THE ELECTROLYSIS OF
MOLTEN SODIUM CHLORIDE. 46
Q - 9) DIFFERENCE BETWEEN PRIMARY CELL AND SECONDARY CELL. 47
Q - 10) DESCRIBE THE PROCESS OF NICKEL PLATING. 48
Q - 11) DESCRIBE THE PROCESS OF CHROMIUM PLATING. 48
Q - 12) WHAT IS THE FUNCTION OF SALT BRIDGE OR POROUS PARTITION IN AN ELECTROCHEMICAL CELL? 49
Q - 13) PREDICT WHAT WOULD BE FORMED (I) AT THE ANODE AND (II) AT THE CATHODE WHEN EACH OF THE FOLLOWING MOLTEN
SALTS IS ELECTROLYZED USING INERT ELECTRODES. 49
Q - 14) WRITE DOWN THE USES OF ELECTROLYSIS. 49
Q - 15) DEFINE ELECTROCHEMICAL CELL. 49
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Q - 16) WHICH OF FOLLOWING PAIRS OF TERMS HAVE THE SAME MEANINGS AND WHICH HAVE DIFFERENT MEANINGS? 49
Q - 1) DEFINE THE FOLLOWING TERM: 50
Q - 2) WRITE DOWN THE IMPORTANCE OF PH. 50
Q - 3) STATE BRONSTED LOWRY THEORY OF ACIDS AND BASES AND EXPLAIN IT WITH EXAMPLE OF HCL AND NH3. 51
Q - 4) STATE LEWIS CONCEPT OF ACIDS AND BASES AND EXPLAIN IT WITH EXAMPLE: 52
Q - 5) WHAT IS ARRHENIUS THEORY OF ACID AND BASES WHY IS THE ARRHENIUS THEORY NOT SATISFACTORY FOR ACIDS AND
BASES: 52 Q - 6) WRITE DOWN THE PHYSICAL AND CHEMICAL PROPERTIES OF ACIDS AND BASES: 53
Q - 7) WHAT IS SALT AND EXPLAIN ITS FOUR EXAMPLES: 54
Q - 8) WHAT IS CHEMICAL REACTION DEFINE AND GIVE ONE EXAMPLE EACH OF THE FOLLOWING (I) NEUTRALIZATION (II)
HYDROLYSIS 54 Q - 9) EXPLAIN WITH ILLUSTRATION THAT WHAT ARE STRONG ACID AND BASE AND WEAK ACID AND BASE. ALSO WRITE FORMULAS
OF THEM: 55 Q - 10) SULPHURIC ACID (H2SO4) IS STRONG ACID. H2SO4
- IS WEAK ACID ACCOUNT FOR THE DIFFERENCE IN STRENGTH: 55
Q - 11) GIVE AN EXAMPLE OF MONO-PAROTIC, DI-PAROTIC AND TRI-PAROTIC ACID: 55
Q - 12) DEFINE ACIDIC, BASIC AND NEUTRAL SOLUTIONS IN TERMS OF H+ ION CONCENTRATION. INDICATE WHETHER EACH OF THE
FOLLOWING SOLUTION WILL BE ACIDIC, BASIC OR NEUTRAL: 56
Q - 13) DEFINE MOLARITY. WHAT IS MOLAR SOLUTION? 56
Q - 14) DEFINE TERM AMPHOTERIC AND GIVE EXAMPLE? 56
Q - 15) GIVE AN EQUATION TO SHOW THE DISSOCIATION OF WATER? 56
Q - 16) DEFINE PH? EXPLAIN WHY A NATURAL SOLUTION IS SAID TO HAVE A PH OF 7? 57
Q - 17) DESCRIBE THE COMMERCIAL PREPARATION AND USES OF SALTS? 57
Q - 18) DEFINE ACID – BASE TITRATION, STANDARD SOLUTION AND EQUIVALENCE POINT? 59
Q - 19) IDENTIFY THE FOLLOWING AS A WEAK OR STRONG ACIDS OR BASES? 60
Q - 20) DESCRIBE CLEARLY HOW A SOLUTION OF HCL COULD BE TITRATED WITH A SOLUTION OF NAOH? 60
Q - 1) DEFINE THE FOLLOWING TERM: 61
Q - 2) DEFINE A THERMOCHEMICAL REACTION. WHAT IS MEANT BY ENTHALPY OF A REACTION? ALSO DEFINE EXOTHERMIC
REACTION WITH TWO EXAMPLES: 61
Q - 3) DEFINE ENDOTHERMIC REACTION AND ALSO GIVE TWO EXAMPLES ENDOTHERMIC REACTION? 62
Q - 4) DEFINE HEAT OF NEUTRALIZATION: WHAT WOULD BE THE VALUE OF REACTION OF NEUTRALIZATION WHEN STRONG ACID
REACTS WITH STRONG BASE? 62
(i) HEAT CONTENT (ENTHALPY): ........................ 61 (ii) HEAT OF NEUTRALIZATION: ........................ 61
(iii) THERMOCHEMISTRY: .................................... 61 (iv) EXOTHERMIC REACTION: ............................. 61
(v) ENDOTHERMIC REACTION: ............................. 61
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Q - 1) Define chemistry? Write the name of its branches: Ans: Chemistry is the branch of science that deals with the properties, compositions and structure of matter. It also deals with principles and the laws governing the changes involved in the matter. The names of its branches are as follow:
1. Physical chemistry 2. Organic chemistry 3. Inorganic chemistry 4. Bio chemistry 5. Analytical chemistry 6. Industrial or applies chemistry 7. Nuclear chemistry 8. Polymeric chemistry 9. Environmental chemistry
Describe the branches of chemistry: Physical chemistry: It deals with the laws and principles governing the combination of atoms
and molecules in chemical reactions. Organic chemistry: It is the study of hydrocarbons and their derivatives. It also deals with
carbon compounds with the exception of CO2, CO etc.
Inorganic chemistry: It is the study of elements and their compounds generally obtained
from non – living organisms i.e. minerals.
Biochemistry: It is the study of compounds of living organism i.e. plants, animals and their
metabolism in the living body. Analytical chemistry: It is the study of methods and techniques involved to determine kind,
quality and quantity of various components in given substance.
Industrial or Applied chemistry: It is the study of different chemical processes
involved in the chemical industries for the manufacture of synthetic products like glass,
cement, paper, soda ash, fertilizers, medicines etc.
Nuclear chemistry: It is the study of changes occurring in the nuclei of atoms,
accompanied by the emission of invisible radiations.
Polymeric chemistry: It is the study of polymerization and the products obtained
through the process of polymerization such as plastic, synthetic fibbers, papers etc.
Environmental chemistry: It is the study of interaction of chemical materials and
their effects on the environment of animals and plants.
Q - 2) What is scientific method? Define Hypothesis and Theory. A particular method that is used to search for facts and figures is called
Scientific Method. It consists of observation, hypothesis, theory and scientific laws.
It may be possible answer of the problems after observation. It is also a trail idea for accumulating more knowledge or facts.
It is the verified result of hypothesis, which is obtained with the help of careful experimentation.
chemistry INTRODUCTION TO CHEMISTRY Chapter
IX One
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Q - 3) What is Scientific method? Write the name of its four stages and describe them:
Scientific Method: A specific method that is used to search for truth or facts. In addition: It is based on observation, hypothesis, theory and scientific laws. Observation: It is the basic tool for explaining a phenomenon but it may vary from person to person according to his skill. Hypothesis: The statement may be possible answer of the problems after observation. It is also the trail idea for accumulating of more knowledge or facts.
Theory: It is the verified results by hypothesis, which is obtained with the help of careful experimentation. Scientific law: When a theory is tasted repeatedly and is found to fit according to facts, gave valued predictions is called Scientific law. Q - 4) Write down the contribution of Muslim scientists in the field of
Chemistry: Jabir – ibne – Hayyan: (721 – 803 A.D.) He is known as the father of chemistry. He invented experimental methods for preparation of Nitric acid, Hydrochloric acid and white
lead. He developed method for extraction of metal from their ores. He developed method for dyeing clothes.
Al – Razi: (862 – 930 A.D.) He was physician, surgeon, philosopher & alchemist. He was the first person who used opium as an anaesthesia. He prepared ethyl alcohol by fermentation process. He divided the substances into living and non- living origins.
Al – Beruni: (973 – 1048 A.D.) He contributed in mathematics, physics, chemistry,
metaphysics, geography and history. He determined the densities of different substances.
Ibne – Sina: (980 – 1037A.D.)
He contributed in the field of mathematics, medicine, medical
chemistry, philosophy and astronomy.
Q - 5) What is scientific law?
Scientific Law: When a theory is tasted repeatedly and found to fit according to facts, and gave valued predictions is called Scientific Law.
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Q - 6) Write down the contributions of Modern scientists in the field of Chemistry:
Robert Boyle: (1627 – 1961 A.D.) He is known as father of modern chemistry. He was first to put forward the idea that chemistry should be regarded as a systematic
investigation of nature promoting knowledge. He tried to purify chemicals to obtain reproducible reactions. J. Priestly: (1733 – 1804 A.D.) He discovered oxygen, Sulphur dioxide and hydrogen chloride. J. J. Berzelius: (1779 – 1848 A.D.)
He introduced the idea of symbols, formulae and chemical equation to make the study more systematic.
Arrhenius: (1859 – 1927 A.D.) and M. Faraday: (1791 – 1867 A.D.)
They both gave the Ionic theory and Laws of electrolysis. Scheele: (1742 – 1786 A.D.)
He discovered chlorine. J. Black: (1728 – 1799 A.D.)
He made study of carbon dioxide Cavendish: (1731 – 1810 A.D.)
He discovered Hydrogen. John Dalton: (1766 – 1844 A.D.)
He gave atomic mass theory. Mendeleev: (1824 – 1907 A.D.)
He discovered the periodic arrangements of elements.
Lavoisier: (1743 – 1794 A.D.)
He discovered that oxygen constituted about one-fifth of air.
Q - 7) What important role chemistry plays in the society:
Ans: Chemistry plays very important role in the society to prepare such as food, synthetic fibbers, plastics, medicines, soap, detergents, cosmetics, cement, fertilizers, glass etc.
Q - 8) Write three significant reasons to study chemistry?
It has important practical applications in the society the development of life saving drugs is one and complete list would touch upon most areas of modern technology.
It is an intellectual enterprise, a way of explaining our material world. It figures prominently in other field, such as in biology in the
advancement of medicines and useful intellectual tool for making important decisions.
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Q - 1) Sate the following laws:
“It states that in any chemical reaction the initial weight of reacting substances is equal to the final weight of the products.”
“It states that the different samples of the same compound always contain the same elements combined together in the same proportions by mass.”
“It states that if two elements combine to form more than one compound. The masses of one element that combine with a fixed mass of the other element are in the ratio of small whole numbers or simple multiple ratios.”
“It states that the two different elements separately combine with the fixed mass of third element, the proportions shall be either in the same ratio or simple multiple of it.” Q - 2) State law of conservation of mass with Landolt’s experiments:
Law of conservation of Mass: “It states that in any chemical reaction the initial weight of reacting substances is equal to the final weight of the products.”
Landolt’s experiment: German Chemist H. Landolt’s has tested different chemicals to verify Law of conservation of mass. 1. He took H – shaped tube that has two limbs.
2. He filled limbs A and B with Silver Nitrate
(AgNO3) & Hydrochloric acid (HCl) respectively. 3. The tube was sealed and weighted initially. 4. The reactants were mixed by inverting and
shaking the tube. 5. After mixing the tube weighted again and he
observed that weight, remain same.
Chemical Reaction: AgNO3 + HCl → AgCl + HNO3
Q - 3) State the law of Constant proportion with example?
Law of Definite proportions: “It states that the different samples of the same compound always contain the same elements combined together in the same proportions by mass. Example: Every sample of pure water, through prepared in laboratory or obtained
from rain, river, or water pump contains one part of Hydrogen (H) and eight
parts of Oxygen (O). Like H2O = 2 : 16 or 1 : 8
chemistry CHEMICAL COMBINATION
Chapter
IX TWO
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Q - 4) State the law of multiple proportions with example:
Law of Multiple proportions: “It states that if two elements combine to form more than one compound. The masses of one element that combine with a fixed mass of the other element are in the ratio of small whole numbers or simple multiple ratios.” Example: Carbon (C) form two stable compounds with Oxygen (O) namely carbon
monoxide (CO) and carbon dioxide CO2.
Compound Mass of Carbon (C) Mass of Oxygen(0) Ratio of Oxygen (0)
CO 12 16 1 CO2 12 32 2
Q - 5) State the law of Reciprocal proportion with example? “It states that the two different elements
separately combine with the fixed mass of third element, the proportions shall be
either in the same ratio or simple multiple of it.”
Example:
When two elements Carbon
(C) and Oxygen (O) separately combine
with fixed mass of Hydrogen (H) to
form methane CH4 and water H4O.
Ratio of H is 1 in CH4 & H2O
Ratio of C is 3 in CH4 & CO2
Ratio of O is 8 in H2O & CO2
H
CH4 H2O
12 : 4 2 : 16
3 : 1 CO2 1 : 8
C
O 12 : 32
3 : 8 Q - 6) What is Einstein theory? & Write reaction B/W mass & energy:
Einstein Theory: The famous physicist and mathematician Albert Einstein proposed the
relation between mass and energy. i.e. “There is no detectable gain or loss of mass in
a chemical reaction”.
Mathematically E = mc2 where “E” is energy, “m” is mass and “c” is speed of light.
Q - 7) What is chemical reaction? Define and give example each of the following:
Chemical Reaction: It is a change in which the composition of substances is changed and new substances formed. It has five types as follows. (1) Decomposition Reaction: It is the reaction in that breaks down a
compound or chemical substances to form two or more substances.
Heat
CaCO3 CaO + CO2
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(2) Addition Reaction: It is the reaction in which two or more substances combine together to form new substances.
Example: CaO + CO2 CaCO3
Example: Na + Cl2 2NaCl
(3) Single Displacement Reaction: It is the reaction in which one atom or a group of atoms of a compound replaced by another atom or group of atoms.
Example: 2Na + 2H2O 2NaOH + H2
Example: Zn + 2HCl ZnCl2 + H2
(4) Double Displacement Reaction: It is the reaction in that two compounds exchange their partners to form new compounds.
Example: NaCl + AgNO3 NaNO3 + AgCl
Example: CaCl2 + Na2CO3 2NaCl + CaCO3
(5) Combustion Reaction: It is the reaction in that substances react with either free oxygen or oxygen of air, with rapid release of heat and flame.
Example: CH4 + O2 CO2 + 2H2 + ∆H (Heat)
Example: C + O2 CO2 + ∆H (Heat) Q - 8) What is chemical reaction? Define & give one example each:
(1) Addition reaction (2) Double Displacement reaction
Chemical Reaction: It is a change in which the composition of substances
changes to forms new substances. (1) Addition Reaction: It is the reaction in which two or more substances
combine together to form new substances. Example: CaO + CO2 CaCO3
(2) Double Displacement Reaction: It is the reaction in which, two
compounds exchange their partners to form new compounds. Example: NaCl + AgNO3 NaNO3 + AgCl
Q - 9) What is chemical reaction? Define & give one example of each:
(1) Combustion reaction (2) Single Displacement reaction
Chemical Reaction: It is a change in which the composition of substances is changed and new substances formed.
(1) Combustion Reaction: It is the reaction in which, substances react with either free oxygen or oxygen of air, with rapid release of heat and flame.
Example: CH4 + O2 CO2 + 2H2 + ∆H (Heat)
(2) Single Displacement Reaction: It is the reaction in which one atom or a group of atoms of a compound replaced by another atom or group of atoms.
Example: 2Na + 2H2O 2NaOH + H2
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Q - 10) What is Empirical formula? Give an example:
Empirical Formula: (E.F) The formula that describes the smallest or least ratio
of the combining atoms of different elements presents in a molecule.
Example: The empirical formula of Benzene is CH Mathematically
Example: The empirical formula of Glucose is CH2O 𝑬. 𝑭 =𝑴.𝑭.
𝒏
Q - 11) What is Molecular formula? Give an example:
Molecular Formula: (M.F) The formula that describes actual number and type
of the combining atoms of all elements presents in a molecule. Example: The molecular formula of Benzene is C6H6 Mathematically
Example: The molecular formula of Glucose is C6H12O6 𝑴.𝑭 = (𝑬.𝑭)𝒏
Q - 12) Define the following: (i) Atomic
mass (ii) Mole
(iii) Molar Mass
(iv) Avogadro’s Number
(i) Atomic mass: It is the average mass of naturally occurring isotopes that
compares to the mass of one atom of Carbon – 12 a.m.u.
(ii) Mole: It is amount of substances contains as many elementary particles
like atoms, ions, molecules etc. It is denoted by n. Formula n =m
M
(iii) Molar mass: It is the mass in grams of one mole of substances. Such as
(molecular mass, formula mas, atomic mass) etc.
(iv) Avogadro’s number: It is a constant number that is equal to 6.02 × 1023
of one mole of any substances. It is denoted by NA. Q - 13) Can one substance have the same empirical formula and molecular
formula? Explain with examples:
Ans: Yes, one substance can have the same empirical formula and molecular
formula because they have the simplest and least whole number and have no
difference between their molecular and empirical formulas.
Example: Name Empirical Formula Molecular Formula
Sodium Hydroxide NaOH NaOH Sugar C12H22O11 C12H22O11 Methane CH4 CH4 Potassium Nitrate KNO3 KNO3
13
Q - 14) What is chemical equation? What is a co-efficient and expression? Give an example of balance equation:
Chemical Equation: It is short hand method of describing the chemical reaction, in terms of symbols and formulae of the substances involved in a chemical reaction. Co – efficient: The number, in front of the formulas in a chemical equation is
called Co – efficient. It is present before molecule or atoms. Expression: The latters, (g), (l) and (s) are placed as subscript indicates the states of products and reactants.
Balanced Equation:
Example: MnO2
2KClO3 (S) 2KCl(s) + 3O2(g) Q - 15) The value of carbon in periodic table is 12.011 a.m.u rather than
12.00 a.m.u. Explain it:
Ans: The value of carbon in periodic table is 12.011 a.m.u rather than 12.00 a.m.u because naturally Carbon has two isotopes C – 12 with 98.889% and C- 13 with 1.111. Thus, the atomic mass of Carbon (C) atoms becomes 12.011 a.m.u.
Average/Sum of Carbon isotopes =12×98.889+13×1.111
100= 12.011a.m.u.
Q - 16) Differentiate Empirical formula and molecular formula:
Empirical formula Molecular formula
It describes smallest or least ratio of the elements in compound.
It describes actual number and type of elements in compound
Some compound may have same empirical formula.
No, any two compounds may have the same molecular formula.
Example: Empirical formula of Acetic acid and glucose is same as CH2O
Example: Molecular formula of Acetic acid is CH3COOH and Glucose is C6H12O6
Molecular mass Formula mass
The term molecular mass cannot be used with ionic compounds because there are no discrete molecule in ionic compounds.
The term formula mass can be used with either molecular compounds or ionic compounds.
It is the sum of atomic masses of all atoms in a molecular formula of substances.
It is the sum of atomic masses of all atoms in a formula unit of substances.
Molecular mass of CO2 is 44 a.m.u. Formula mass of NaCl is 58.5 a.m.u.
14
Q - 1) Write down the main postulates of Dolton Atomic theory:
Dolton Atomic Theory:
All elements are made up of small invisible, indestructible particles are called atoms. All atoms of a given element are identical in all respects having same size, mass and
chemical properties. However, the atoms of one element differ from the atoms of other element.
Compounds are formed when atoms of more than one element combine in a simple whole number ratio.
A chemical reaction is a rearrangement of atoms but atoms themselves are not changed this means that atoms are neither created nor destroyed in chemical reactions.
Q - 2) Describe Modern Atomic theory:
Modern Atomic Theory: According to modern atomic theory, Atom is a complex organization and composed of even smaller particles called sub – atomic particles (Fundamentals particles). They are Electrons, Protons and Neutrons. Q - 3) Write down the properties of Cathode Rays? Properties of Cathode Rays:
i. They cast shadows of objects towards anode and travels in straight lines.
ii. They cause a light paddle wheel to rotate. Showing that they are material particles.
iii. They are negatively charged particles and deflected towards positive plate.
iv. The (Charge/Mass) e/m ratio of them is 1.7588 x 108 c/g.
v. They possess Kinetic Energy so they can produce mechanical pressure.
vi. They are invisible cause some material to glow or produce fluorescence.
Q - 4) Write down the properties of Positive Rays?
Properties of Positive Rays: i. They also travel in straight line from anode to cathode.
ii. They cause a light paddle wheel to rotate. Showing that they are material particles.
iii. They are positively charged particles and deflected towards negative plate.
iv. The (Charge/Mass) e/m ratio of them is much smaller than electrons.
v. Their e/m ratio varies with the nature of gas in the tube.
vi. They have +1.6022 x 10–19 coulomb charge.
CHEMISTRY ATOMIC STRUCTURE
CHAPTER
IX THREE
15
Q - 5) Describe the discovery of electrons (Cathode Rays)
Discovery of Electrons:
The British physicist J.J. Thomson discovered
electrons by an experiment in 1897. For that he used
a glass tube (Discharge tube) fitted with two metal
electrodes connected to a high voltage source and a
vacuum pump.
He evacuated the tube and passed a current of high potential between the electrodes at very low pressure.
He observed that streaks of bluish light extending from negative electrode (cathode) towards positive electrode (anode).
These rays travelled in straight line and glow at the opposite end where they stroked.
He showed that these rays were deflected towards the positive plate in electric and magnetic field.
He named the rays “Electron” and they have negative (–) charge.
Q - 6) Describe the discovery of Protons: (Positive Rays) what are protons and how were these produced?
Discovery of Protons:
The German physicist Goldstein discovered
protons by an experiment in 1886. For that, he
used a glass tube (Discharge tube) with
perforated cathode, fitted two metallic electrodes
connected to a high voltage source.
He conducted a series of process during his experiment. He perforated cathode containing a gas at low pressure and passed current with high potential source.
He observed that rays containing of positively charged particles travelled from anode to cathode. These rays also travelled in straight line towards negative plate.
He showed that positively charged particles was equal to negatively charged particles.
He named these rays “Protons” and they have positive (+) charge.
16
Q - 7) Describe the discovery of Neutrons:
Discovery of Neutrons:
The English physicist James Chadwick discovered Neutrons through artificial radioactivity in 1932. For that he bombarded Be (Beryllium) with alpha particles, neutrons were appeared. Q - 8) Describes the properties of electron, proton and neutron: Electron:
Electron is negatively charged particle. It has electric charge about – 1.602 x 10 – 19 coulombs. It moves around the nucleus.
It has 9.109 x 10 –31 kg mass. i.e. 1
1836 Of protons.
Proton: Proton is positively charged particle. It has electric charge about + 1.602 x 10 – 19 coulombs. It lies in the nucleus. It has 1.672 x 10 –27mass. i.e. 1836 times of electron.
Neutron: Neutral particle has no charge. It lies in the nucleus. It has 1.762 x 10 –27mass. i.e. 1836 times of electron.
Q - 9) What are the names of sub – atomic particles? What are the masses in atomic mass units (a.m.u) and what is unit charges each?
Ans: The names of three Subs – atomic particles are electron, proton and neutron.
Electron: Its mass is 0.0005485 a.m.u and unit charge +1. Proton: Its mass is 1.007276 a.m.u and unit charge –1. Neutron: Its mass is 1.008664 a.m.u and unit charge 0 (None). Q - 10) Define (i) Isotopes (ii) Mass number (iii) Atomic number
Isotopes: Atoms of the same element having the same atomic number but
different atomic masses are called isotopes.
Such as Protium H11
, Deuterium D12
and Tritium T13 are isotopes of Hydrogen (H).
Mass Number: The total sum of the protons and neutrons in the nucleus of an atom is
called the mass number and it is denoted by A.
Atomic Number: The number of protons in the nucleus or number of electrons outside the
nucleus of an atom is called atomic number and it is denoted by Z.
17
Q - 11) What is meant by Radioactivity? Draw a labelled diagram showing the separation of Alpha, Beta and Gamma rays: And also write the properties of each:
Radioactivity: The process in which emission of fundamental particles, in the form of radiations takes place is called radioactivity.
The British physics Ernest Rutherford in 1902 determined the nature of radioactive rays by an experiment and showed that it is composed of three types of rays. For that, he placed a sample of radioactive substances in a lead block, between the two oppositely charged plates. The radiations resoled into three components.
First component deflected towards negative plate, having (+) charge & name as α– rays.
Second component was deflected towards positive plate, having (–) charge & name as β– rays.
Third component did not deflect towards any plate, having no charge & name as γ– rays.
𝜶 – i. 𝛼– Rays deflect towards negative plate, and having (+3.2 × 10−19 𝑐 ) charge. ii. They have heavy masses that are why they cannot pass through thick metal
foil. iii. They are strong ionizing agents. iv. They are Helium nuclei.
𝜷 – i. 𝛽– Rays deflect towards positive plate, and having (−1.6 × 10−19 𝐶 ) charge. ii. They have great power to penetrate that is why they can also pass through
thick metal foil. iii. They are weak ionizing agents. iv. They are electrons.
𝜸 – i. 𝛾 – Rays do not deflect towards any plate, and they are neutral. ii. They have greater power to penetrate that is why they can pass through
thicker metal foil than 𝛽 – rays.
iii. They are weaker ionizing agents than 𝛽 – rays. iv. They are electromagnetic radiations.
18
Q - 12) Describe the Rutherford’s experiment, which led him to the
discovery of the nucleus of an atom? Or Describes Rutherford’s experiment of Gold metal foil:
Discovery of Nucleus:
Rutherford discovered Nucleus of an atom by an experiment in 1911. For that, he used Gold metal foil and Alpha particles.
He bombarded a beam of alpha 𝛼 – particles through a very thin gold metal foil.
He observed that most of alpha 𝛼 – particles passed through it without any deflection. Some of them deflected at large angles and very few of them bounced back.
He concluded two things Volume and presence of Nucleus.
The volume occupied by an atom must be largely empty as most of the 𝛼 – particles passed through the foil unbounded.
The positive charge, in the atom is concentrated in extremely dense region that he called the nucleus.
Rutherford atomic model: According to him, an atom consists two parts.
(i) Nucleus (ii) Extra Nuclear part Nucleus: It has positive (+) charge because proton and neutron
reside in it. The weight of an atom is concentrated in the
nucleus. Extra nuclear part: The electron is revolving around the nucleus in the
extra nuclear part in various orbits, which are also called as shells or energy levels.
Defects of atomic model: Electrons are continuously revolving around the nucleus that may cause
lose their energy and fall into nucleus. If revolving electrons emit energy continuously, then there would be a
nonstop spectrum but we get it from the atoms of elements.
19
Q - 13) Explain Neil Bohr’s Atomic theory:
Neil Bohr’s atomic theory: The Danish physicist offered theoretical assumptions for atomic structure in
1913. The important assumptions are as following. i. Electrons in atoms move only in certain allowed energy levels (energy states) so
they will not fall in the nucleus. ii. The atom radiates energy as light when the electron jumps higher energy level (E2)
to lower energy level (E1).
iii. The quantity of energy radiated is in discrete quantity, called Quanta.
iv. A quantum of energy is directly proportional to the frequency of radiation.
i.e. ∆𝐸 = 𝐸2 − 𝐸1 = ℎ𝑣
Where ℎ = Planks constant and 𝑣 = frequency of radiation.
Q - 14) Write down the application of Isotopes:
Application of Isotopes or Uses of isotopes: i. Isotopes use as tracers in physical, chemical and biological researches. ii. Isotopes also use in treatments and diagnoses of disease like cancer. Q - 15) C – 14 and N – 14 both have same mass number yet they are different elements, Explain:
Ans: C – 14 and N – 14 both have same mass number yet they are different
elements because of their different atomic numbers as atomic number of
Carbon is 6 and Nitrogen is 7 and C – 14 is isotope of Carbon.
Q - 16) In what way isotopes of a given element differ from each other.
Ans: It is because that the different isotopes of the same elements differ only in the number of neutrons in the nucleus of an atom. Q - 17) What are isotopes? Write the symbol of Protium, deuterium and tritium with their atomic numbers and mass numbers.
Isotopes: Atoms of the same element having the same atomic number but different atomic masses called isotopes.
Name of Isotopes Symbols Atomic Number Mass number
Protium H11 H 1 1
Deuterium D12 D 1 2
Tritium T13 T 1 3
20
Q - 1) Define the following: (I) DOBERNEIR’S RULE OF
TRAID
(II) MODERN PERIODIC LAW
(III) ELECTRONEGATIVITY
(IV) PERIODICITY
(V) ATOMIC RADII
(VI) IONIZATION ENERGY
(VII) PERIOD
(VIII) ELECTRON AFFINITY
(IX) GROUP
i. Doberneir’s Rule of traid: It states, “Central atom of each set of traid
had an atomic mass almost equal to the arithmetical mean of the atomic
masses of the two elements.”
ii. Modern Periodic law: It states, “The physical and chemical properties of
elements are periodic functions of their atomic weight”.
iii. Periodicity: The repetition of Physical and Chemical properties of elements
periodically is called periodicity of elements.
iv. Electronegativity: The relative power of an atom to attract the shared
pair of electrons towards itself is called electronegativity. The most
electronegative atom is Florien (F) with electronegativity = 4.
v. Electron Affinity: It is defined as the energy change that occurs when an
electron is gained by an atom on the gaseous state.
vi. Atomic Radii: It is defined as half the distance between two adjacent nuclei
of two similar atoms in touch with each other. It is measured in Angstrom
unit Ao.
vii. Ionization Energy: It is defined, as the minimum energy required removing
an electron from a gaseous atom in its ground state. It is measured in K.Jol/Mol or Electron volt per atom. Ev/atm.
viii. Period: The modern periodic table contains seven horizontal rows called
periods. The elements within a period have dissimilar properties from left to
right.
ix. Group: The modern periodic table contains sixteen vertical columns called
groups. It is divided into two groups A and B. the elements of Group A are called main or representative elements. In addition, elements of Group B are called
Transition Elements.
chemistry PERIODICITY OF ELEMENT
Chapter
IX Four
21
Q - 2) Write characteristics Metals, Non – metals and Metalloids: Metals:
(i) They are electropositive and lose electrons to form cat – ions.
(ii) They are basic oxides and good conductors of heat and electricity.
(iii) All of them have lustre and are malleable and ductile.
Non – Metals: (i) They are electronegative and Gain electrons to form an – ions.
(ii) They are acidic oxides and bad conductors of heat and electricity.
(iii) Most of them are gases and have no definite shape and volume.
Metalloids: (i) They have dual character and shows properties of both metals and non - metals.
(ii) They have basis as well as acidic nature.
(iii) They are semiconductors and brittle rather than malleable.
Q - 3) Describe properties of Transition elements: (Group IB to VIIB)
(i) They are metals and they have incomplete valence shall.
(ii) In chemical reactions, they show more than one valences.
(iii) These elements in compounds having characteristic colors.
(iv) They have ability to form complex ions by coordination.
Q - 4) Describe the properties of Group I A, to Group VIII A:
Group I – A: (Lithium Family / Alkali Metals)
They are called alkali metals because they form water-soluble base such as NaOH, KOH.
Their atomic radii, atomic volumes, ionic radii increase from Li to Cs.
Their melting and boiling point decrease downward.
They are highly reactive metals with low melting points.
This group contains Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Caesium (Cs)
and Francium (Fr).
Their valance shell contains only one electron and they lose it in chemical reactions. Group II – A: (Beryllium Family / Alkaline Earth Metals)
They are called alkaline earth metals and they are a bit harder, have higher melting and boiling
point.
Their valance shell contains only two electron and they lose them in chemical reactions.
They have smaller atomic radii, atomic volumes than Alkali metals.
Downward they do not show a regular trend in melting, boiling points and densities.
This group contains Beryllium (Br), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba) and
Radium (Ra).
22
Group III – A: (Boron Family)
They are highly reactive elements except Boron (Br), having metallic character.
Their valance shell contains only 3 electrons. It means their valance is +3
They have moderate tendency to form compounds. Born is metalloid having properties
of metal and non – metal.
Downward they decrease their ionization potential and increase size of atoms.
This groups contains Boron (B), Aluminium (Al), Gallium (Ga), Indium (In) and thallium (Tl)
Group IV – A: (Carbon Family)
They are highly reactive elements except Boron (Br), having metallic character.
Their valance shell contains 4 electrons, except Tin (Sn) and Lead (Pb) exhibit a variable
valance 2 and 4.
The elements of this group are metal, non – metal and metalloid. Such as Sn and Pb are
metals, C is non – metal and Si and Ge are metalloids.
Down the group, their atomic radii and volumes increase due to addition of new shells.
Carbon (C) and Tin (Sn) exist in different allotropic forms.
This groups contains Carbon (C), Silicon (Si), Germanium (Ge), Tin (Sn) and Lead (Pb)
Group V – A: (Nitrogen Family)
Their valance shell contains 5 electrons. Nitrogen have tendency to except three
electrons and forms number of oxides as NO, NO2, N2O4 etc.
The elements of this group are metal, non – metal and metalloid. Such as Bi is metal, N
and P are non – metals and As and Sb are metalloids.
The elements of this group are quite reactive, having quite tendency to form compounds.
Except Nitrogen (N) all exist in more than one allotropic form.
This group contains Nitrogen (N), Phosphorus (P), Arsenic (As), Antimony (Sb) and Bismuth
(Bi).
Group VI – A: (Oxygen Family)
Their valance shell contains 6 electrons. Oxygen (O) and Sulphur (S) form divalent
negative ions O2- and S2-
The elements of this group are metal, non – metal and metalloid. Such as (Po) is metal,
O and S are Non – metals and Se and Te are metalloids.
The elements of this group are quite reactive, having quite tendency to form compounds.
All of them exhibit the property of allotropy.
This group contains Oxygen (O), Sulphur (S), Selenium (Se), Tellurium (Te) and Polonium
(Po).
23
Group VII – A: (The Halogens)
Their valance shell contains 7 electrons. Oxygen (O) and Sulphur (S) form divalent
negative ions O2- and S2-
Except Astatine (At) which is metalloid, All other are non – metals and exist as diatomic
molecules.
They have high ionization energies and large negative electron affinities.
They easily accept an electron to form halide ions i.e. F1-, Cl1- Br1- and I1-
All of them exhibit the property of allotropy. Such as Oxygen (O2)and Ozone (O3)
This group contains Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I) and Astatine (At).
Group VIII – A: (Inert and Noble Gases)
Their valance shell contains 8 electrons. Except helium (He) which has two electrons.
They are mono atomic and exist in gaseous state.
With exception of Krypton (Kr) and Xenon (Xe) are slightly reactive under drastic condition
and rest all of them are very inert chemically.
They are mostly chemically non – reactive because of great stability.
This group contains Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe) and Radon
(Rn). Q - 5) If an element contains two shells only and its outer most shell contains five electrons then to which group the element belongs in the periodic table. Name the element. Predict its period.
Ans: If an element contains two shells only and its outer most shell contains five electrons then the element belongs to group VA in the periodic table. The name of element is Nitrogen (N) and its period is 2.
Q - 6) What do you mean by long form of periodic table? Explain some of its application:
Ans: The modern periodic table is known as the long form of periodic table because elements are arranged in order of increasing atomic number. It contains seven horizontal rows called periods and sixteen vertical columns called groups. Application of periodic table:
Prediction of new elements and their chemical characteristics is now possible.
The classification of elements into periods and groups simplifies the study of chemistry.
Suggestion for further research becomes available now. Reactivity of elements can be visualized.
24
Q - 7) Discuss some of the physical properties of the elements which exhibit periodicity.
Ans: The physical properties of elements depend upon boiling point, melting point, densities, electric conductivity and hardness. Physical Properties of elements: The elements of group IA, IIA, IIIA, IVA, VA, and VIA are metals and conduct electricity.
The atomic radii increase down the group due to addition of new shell in each atom.
Melting and boiling points in group IA decrease gradually from top to bottom
The elements are at right side Non – metals, at left side are metals and in the middle are
metalloids.
Q - 8) How does the modern periodic law differ from Mendeleev’s periodic law? Explain groups and periods in modern periodic table: Ans: According to The Modern periodic law “The physical and chemical properties of all elements are periodic functions of their “Atomic numbers” while By Mendeleev’s
periodic law “The physical and chemical properties of elements are periodic function of their Atomic weights”. Groups: The modern periodic table contains sixteen vertical columns called groups. It is
divided into two groups A and B. Elements of group “A” are called main or representative
elements. And group B’s elements are called Transition Elements.
Period: The modern periodic table contains seven horizontal rows called periods. The
elements within a period have dissimilar properties from left to right.
Q - 9) What do you understand by periodic classification of elements? What are the merits and demerits of classification of elements:
Ans: According to the periodic classification of elements are arranged in the order of increasing atomic number in period, such that all elements having same number of valence electrons grow under the same vertical column called group. This also ensures periodicity in electronic configuration and in chemical properties.
The classification of element is based on fundamental property of elements.
It explains variations and similarities in the properties of elements in term of
electronic configuration.
It provides clear demarcation of different kinds of elements such as active
metals, metalloids, non – metals, transition elements, inert gases etc.
It relates position of an element to its electronic configuration in the valence
shell.
25
The classification of elements is unable to reflect electronic configuration of many elements in transition group, in lanthanides and actinides.
It fails to accommodate lanthanides and actinides in the main body of the table.
Position of Hydrogen is unresolved. In addition, position of Helium amongst p – block elements is not fully justified.
Q - 10) What do you understand by representative and transition elements? or What do mean by transition elements? Write the general properties/characteristics of transition elements.
Representative elements: The elements of group “A” are called “Main
elements” or “Representative elements” as the properties of these elements are represented by valence electrons.
Transition elements: The elements of group “B” are called “Transition
elements” because the properties of these elements show a gradual change or transition between the two sets of representative elements.
1. These elements have incomplete inner electron shells.
2. They have an ability to form complex ions by coordination.
3. They have strong interred atomic bonds and having characteristics color.
4. They are all metal and having variable valence with similar behaviour.
5. In these elements, penultimate shell is also incomplete.
Q - 11) What are Lanthanides and Actinides? Are they d or f – block elements:
Lanthanides: The Fourteen inner elements of sixth period are called Lanthanides. They start
from Ce to Lu. They have six electronic shells. Actinides: The Fourteen inner elements of seventh period are called Actinides. They start
from Actinium Ac to Lr. They have seven electronic shells.
Q - 12) State Mendeleev’s periodic law. Describe Mendeleev’s periodic table and also write down the merits and demerit of Mendeleev’s periodic table:
Mendeleev’s Periodic Law: Statement: “The physical and chemical properties of elements are a periodic
function of their atomic weights.”
26
SALIENT FEATURES OF TABLE:
It has eight vertical columns called groups and twelve horizontal rows called period.
Elements in each vertical column have similar properties. Vacant spaces were left for the elements not discovered until then. He proposed their names as eka – boron, eka – aluminium and eka –
silicon. The group number indicates the highest valence that can be attained
by elements of that group.
It helps in systematic study of elements and forcefully proved the concept of periodicity.
The prediction of new elements was made possible.
It helped in correcting many doubtful atomic masses.
In his table, there was no place for isotopes of elements.
It fails to give idea of atomic structure.
Dissimilar elements were placed in same group i.e. Alkali metals (Li, Na, K, Rb, Cs, Fr) were
placed with coinage metals (Ag, Cu, Au)
Similar elements placed in different groups. For example, Barium (Ba) and Lead (Pb)
resemble in many properties but they are placed in separate groups.
Q - 13) Explain Newland’s Law of octave. How this law provide the larger scope for the classification of the elements:
Newland’s Law of octave:
Statement: “If elements are arranged in the order of increasing atomic masses the
eight element starting from a give one, has similar properties as first one i.e. its properties is a kind of repetition of the first, like the eight note on an octave of music” Larger Scope for Classification:
Ans: This law provides the larger scope for the classification of elements by the arrangement of its elements with their physical and chemical properties at a regular interval that show the existence of periodicity of the Modern periodic table.
Defects of Newland’s Law:
“Hydrogen” was not included in his sequence.
His sequence was failed because it worked for first sixteen elements.
27
Q - 1) Define Chemical bonding and Discuss how atoms unite and change into molecules:
Chemical Bonding: The Force, which holds atoms together in a molecule or a crystal, is called a chemical bond.
When one electron or more than one electron of any element combines with other or same group of elements, they change into molecules or compound. Example: In combination of NaCl (Sodium Chloride) an atom of Sodium (Na) transfers one outer most shell electron, becomes positive sodium ion (Na+) and an atom of chlorine gains that one electron to complete its octet, and
becomes chloride negative ion (Cl–).
Na(2,8,1) Na+(2,8) + e–
Cl(2,8,7) + e– Cl –(2,8,8)
Na+ + Cl– NaCl
Q - 2) What are the main types of bond? Describe them:
There is two Main type of bond (i) Ionic or electrovalent bond (ii) Covalent bond
Ionic/Electrovalent Bond: In these types of bond, there is a complete transfer of one or more electrons from one atom to another. The atom that transfers electrons gets positive charge and the atom that gains electron gets negative charge. They also called ionic bond because they produce ion and conduct electricity when dissolve in water or melted. Covalent Bond: In these types of bond, each atom has to contribute equal number of unpaired electrons. The shared pair of electrons, which links the atoms in a molecule, is known as covalent bond. In covalent bond, the shared pair of electron is commonly expressed by
single short line (—).
Covalent bond has three types (i) Single covalent bond (ii) Double covalent bond and (iii) Triple covalent bond
CHEMISTRY CHEMICAL BONDING
CHAPTER
IX FIVE
28
Q - 3) Define: (i) Single covalent bond (ii) Double covalent bond and (iii) Triple covalent bond? Or what are the types of chemical bonding?
Single Covalent Bond: In this bond, only one pair of electrons is shared
by the bonded atoms, in which each atom has to share one electron.
This type of bond represents by single short line (–).
For example: Formation of hydrogen H2
Double Covalent Bond: In this bond, only two pairs of electrons are
shared by the bonded atoms, in which each atom has to share two
unpaired electrons. This type of bond represents by double short lines
(=). Formation of Double covalent bonds in O2 Triple Covalent Bond: In this bond, only three pairs of electrons are
shared between the bonded atoms, in which each atom has to share
three unpaid electrons. This type of bond represents by single short
line (≡).
Q - 4) What happens to electrons, when elements combine?
Ans: When elements combines the valence electrons are either transferred from the outer
shell of one atom to the outer shell of another atom or shared between them and it
produces Chemical Bond.
Q - 5) What part of the atom is involved in the formation of chemical bond?
Ans: The outer most part (The valence electrons) of the atoms is involved in
the formation of chemical bond.
Q - 6) Explain with examples? How elements are united by electrovalent bond?
Ans: The elements are unite by electro – Valente bond are one, two or three and
the formation of their bonding is known as single, double or triple covalent bonds
respectively.
Example:
HCl (single covalent bond), CO2 (double covalent bond) and C2H2
(triple covalent bond)
29
Q - 7) What common properties are shown by ionic compound?
Ans: The elements are unite by electrovalent bond one, two or three and the formation
of their bonding is known as single, double or triple covalent bonds respectively.
They held very strong electrostatic forces and they are solids at room temperature.
They have high melting and boiling points.
They are hard and brittle but easily broken.
In solid state, they do not conduct electricity but in liquid state they conduct it.
They are soluble in water (polar) and insoluble in non – polar solvents.
They are non – volatile in nature and generally inorganic compounds.
Q - 8) What is meant by covalent bond? Write electronic formulas of any covalent molecules?
COVALENTBOND: In these types of bond each atom has to contribute equal number of unpaired
electrons. The shared pair of electrons, which links the atoms in a molecule, is known as
covalent bond.
The formation of molecules of CO2 and C2H2.
×
C × ×× ×× ×
C H H ×
H C C H
30
Q - 9) Account for the fact that some covalent bonds are polar and while other is non – polar?
Condition for Non – Polar Covalent Bond: According to the scale of Linus Pauling,
if the difference in the electronegativity of bonded atoms is zero, then the bond is pure Covalent bond
or Non – Polar bond.
Examples:
H – H, O = O, N ≡ N, H3C – CH3, H2C = CH2 and Cl – N – Cl
| Cl
Condition for Polar Covalent Bond: According to the scale of Linus Pauling, if
the difference in the electronegativity of bonded atoms is up to 1.7, then the bond is called
Polar covalent bond or partially ionic in character.
Examples:
H+𝛿 – Cl−𝛿
H+δ – Cl−δ– H−δ
|
H
H |
H – C+δ – Br−δ
| H
H+δ–O−δ |
H+δ
Q - 10) What is co – ordinate covalent bond? Explain with examples:
Co – Covalent Bond: The Co – ordinate covalent bond is formed only when an atom with
an unshared pair of electrons in its valence shell donates a pair of electrons to anther atom
or ion that needs a pair of electrons to acquire a stable electronic configuration.
Examples: The formation of hydronium ion (H3O+) from water molecule and hydrogen ion
(H+) in which the oxygen atom of water acts as donor and hydrogen (H+) ion as accepter.
Donor Accepter Co – ordinate covalent bond
××
H+
××
H – O → H
| H
Formula
H ∙× o ×× H3O+
×
H
31
Q - 11) Define the term covalent bond? How does a covalent bond differ from co – ordinate covalent bond?
COVALENTBOND: In this type of bond, each atom has to contribute equal number
of unpaired electrons. The shared pair of electrons, which links the atoms in a
molecule, is known as covalent bond.
CO – CONALENT BOND: The Co – ordinate covalent bond is formed only when an
atom with an unshared pair of electrons in its valence shell donates a pair of electrons to
anther atom or ion that needs a pair of electrons to acquire a stable electronic configuration.
Covalent bond Co – ordinate covalent bond
1. The mutual sharing of electrons between
atoms forms this.
1. This bond is formed by the one sided
sharing of electrons.
2. This bond is formed between the similar or
dissimilar atoms.
2. This bond formed between two unlike
atoms.
3. The reaction of this bond is denoted by short
line (– ), (=) & (≡).
3. An arrow sign denotes the reaction of this
bond (⟶).
4. They may be polar or non – polar. 4. These bonds are always polar.
5. They are usually insoluble in water 5. They are sparingly soluble in water.
Q - 12) Explain electronegativity with the help of Linus Pauling table:
Electronegativity: The combining power of an atom to attract the shared pair of
electrons towards itself is known as electronegativity.
Explanation:
Linus Pauling proposed the table of electronegativity of different elements, in which he gave
fluorine (Fl) as an arbitrary standard value of electronegativity as 4 because it is most
electronegative element. The electronegativity value of other elements is compared with fluorine.
Values of E.N. of different Elements
Li = 1.0 Be = 1.5 B = 2.0 C =2.5 N = 3.0 O = 3.5 F = 4.0 Na = 0.9 Mg = 1.2
Al = 1.5 Si = 1.8 P = 2.1 S = 2.5 Cl = 3.0 K =0.8 Ca = 1.0 Sc = 1.3 Ti = 1.5
V = 1.6 Cr = 1.6 Mn = 1.5 Fe = 1.8 Co = 1.8 Ni = 1.8 Cu = 1.9 Zn = 1.6 Ga = 1.6
32
Q - 13) Give characteristics of covalent compounds:
They are usually made up of discrete units (molecules) with a weak inter molecular forces.
In solid state there are weak Vander wall forces between the molecules.
They are often gases, liquids or soft solids with low melting points.
They usually have low melting and boiling points.
They are insoluble in water (polar) but soluble in organic solvents like benzene, ether,
carbon tetra chloride etc.
Q - 14) What is chemical bond? Define Ionic Bond. Explain the mechanism of the ionic bond in NaCl (Sodium Chloride)?
Chemical Bond: It is the holding of group of atoms together to form molecules or solids. In addition, it is occurs when a group of atoms can lower its total energy by combining. Ionic or Electrovalent Bond: In this types of bond there is a complete transfer of one or more electrons from one atom to another. Examples: The formation of sodium chloride (NaCl) an atom of (Na) transfers one outer
most shell electron, becomes positive sodium ion (Na+) and an atom of chlorine gains that
one electron to complete its octet, and becomes chloride negative ion (Cl–).
+ –
Na Cl Na+ Cl–
Na(2,8,1) Na+(2,8) + e–
Cl(2,8,7) + e– Cl –(2,8,8)
Na+ + Cl– Na Cl or Na+ Cl–
33
Q - 15) What is coordinate Covalent Bond? How a coordinate covalent bond is formed between ammonia (NH3) and Hydrogen ion (H+) producing ammonium (NH4
+) radical. Explain.
CO – CONALENT BOND: The Coordinate covalent bond is formed only when an
atom with an unshared pair of electrons in its valence shell donates a pair of electrons
to anther atom or ion that needs a pair of electrons to acquire a stable electronic
configuration. Co – ordinate Covalent Bond
H |
H+
H |
H − N − H |
H
Formula
H − N + NH4+
|
H
Q - 16) Define term metal and describe metallic bond?
Metal: It is a substance, consisting of positively charged ions, fixed in a crystal lattice with negatively charged electrons moving freely through the crystal. Metallic bond: It is the combination of electrostatic attraction between the electrons and the positive nuclei of atoms. Q - 17) Explain the following properties of metals:
(i) Luster (ii) Conductivity (iii) Malleability (iv) Ductility
Lustre (Shine): When the portable electrons in metals readily absorb light, falling upon them and move to higher energy levels. When they fall back to their original position, they emit radiation and it caused metal shine. Conductivity: As the electrons in metals are, free to move from one atom to the next they are generally good conductors of electricity and heat. Malleability: It means that metal can be easily bent or hammered into sheets. Ductility: It means that metal can be easily converted into thin wires. Q - 18) Why some metals such as sodium or potassium is soft while other
are hard? Explain:
Ans: It is because in Na or K valence electrons are not confined to any particular atom, instead they are free to move through crystal, and so resulting bond is relatively soft.
34
Q - 19) Explain the origin of dipole – dipole forces between the molecules, and give example:
Dipole – dipole forces: These forces act between polar molecules that possess dipole moments. “A Dipole – dipole force, is an attractive inter-molecular force resulting from the resulting from the inter acting of the positive end of one molecule with the negative end of other.”
Example: The molecule of HCl, Cl has greater electronegativity then H, a partial negative
charge on chlorine (Cl) atom and partial positive charge on Hydrogen (H) atom. The (H+δ– Cl−δ)
has permanent dipole moment.
Q - 20) What do you mean by dispersion forces why are they also called London forces?
Dispersion Forces (London Forces): These forces are the weak attractive forces between temporarily polarized atoms or molecules caused by the varying positions of the electrons during their motion about the nuclei. These forces are also called “London Forces”, because Fritz London first
identified these forces in 1930.
Q - 21) What is Hydrogen bonding? What type of forces, Either Intra – molecular or Inter molecular forces are present in Hydrogen bonding?
Hydrogen Bonding: A hydrogen bond is a dipole – dipole attractive force that exists between
two polar molecules, containing a hydrogen atom covalently bonded to an atom of F, O or N. Water
is best example of Hydrogen bonding. It is denoted by (⋯).
Inter – molecular forces are present in Hydrogen bonding not Intra – molecular forces. Q - 22) What do you mean by Intra – molecular and Inter molecular forces
(Vander Waals’s Forces)?
Intra – molecular forces: These forces hold atoms together in a molecule. For
example, Water (H20) molecule consists of two hydrogen atoms, one oxygen atom join in
a specific way, i.e. covalent bonds.
Inter – molecular forces: They are the attractive forces between the neutral
molecules, which hold them together at certain temperature. These are also called Vender
Waals’s Forces.
35
Q - 1) Define the following term: (i) Solid
(ii) Fusion
(iii) Evaporation
(iv) Sublimation
(v) Boiling point
(vi) Melting point
(vii) Diffusion
(viii) Brownian
Movement
(i) Solid: The state of matter that has definite shape as well as definite volume is known as solid. (ii) Fusion: It is the changing of state from solid to liquid by rising in temperature when heated.
(iii) Evaporation: The escaping of molecules from the surface of liquid when heated is called evaporation. Or It is the changing of state from liquid to gaseous at a certain temperature. (iv) Sublimation: When solids are directly converted into gaseous state during heating this process is called sublimation.
(v) Boiling point: The temperature at which the Vapor pressure of a liquid becomes equal to external pressure applied on the liquid is called boiling point. (vi) Melting point: The temperature at which the solid starts melting is called melting point. (vii) Diffusion: The spreading of substance through medium like air or liquid is
called Diffusion. It is depends upon molar mass or density of substances.
(viii) Brownian movement: A continuous, rapid or zigzag motion of suspended
particles through the medium is called Brownian motion (movement).
Q - 2) Define Kinetic molecular theory and its states of matter: According to kinetic molecular theory matter is
composed of particles which are called molecules. Molecules are in motion and they
possess kinetic energy.
(a) Solid State: In solid state molecules are tightly packed with one another and they
perform only translational motion. Due to this, molecules in solid neither slip nor slide
over one other hence shape and volume of solid is definite.
(b) Liquid State: In liquid state molecules are not tightly packed with one another. Their
positions are not fixed and they can move in all direction, hence liquid does not have any
definite shape and fixed volume.
(c) Gaseous State: In gaseous state, molecules are widely separated from one another and
they move freely in all directions; hence, the shape and volume of gas are not fixed.
chemistry STATES OF MATTER Chapter IX SIX
36
Q - 3) How is solid converted into liquid? Explain it: Conversion of solid into liquid: When a solid is heated, then the kinetic energy of particles
increases and becomes hot. If heating is continued then at certain temperature, the added
energy becomes enough to overcome the attractive forces holding particles of solid in the fixed
positions and it starts melting. At this point solid particles lose their fixed positions as well as
their arrangement and thus solid is converted into liquid.
Q - 4) What do mean by liquid? Describe interchange of liquid to gas: Liquid: The thing that takes the shape of vessel in which it is kept, but does not occupy total
volume available is known as liquid.
Interchange of liquid to gas: when liquid heats the kinetic energy of liquid molecules increases,
its molecules start escaping from the surface of liquid, and Vapour pressure of liquid becomes
equal to external pressure. At this point bubbles of Vapour are able to form within the interior
of liquid and then rise to the surface, where they burst and release Vapour thus the liquid
converts to gas.
Q - 5) What is diffusion? Explain on the basis of kinetic molecular theory:
Diffusion: “The spreading of a substance through medium like air or liquid is called diffusion.” In Liquid by Kinetic Molecular Theory: “According to kinetic theory freedom of
liquid molecules permits diffusion to take place but the closeness of molecules and large number of collisions cause diffusion to be slow.”
In Gas by Kinetic Molecular Theory: “According to kinetic theory molecules of gas are in constant random motion due to which the molecules of gas effuse throughout
the vessel.”
Q - 6) What id Brownian movement? Explain with example:
“A continuous, rapid, zigzag motion of suspended
particles through the medium is called Brownian movement”
Example: Mix some Sulphur in water and stir it, after stirring filter the suspended Sulphur some
of the Sulphur particles are very small and they can pass through the pores of filter paper into filtrate.
Now put a drop of this filtrate on a slide and observe it under high-powered microscope. It is observed
that Sulphur particles perform zigzag motion.”
Explanation: According to kinetic molecular theory, water molecules are always in
motion and they collide with Sulphur particles and push them in some directions where they collide with other water molecules and pushed in some other direction and this process continues.
37
Q - 1) Define the following term: (i) Solution
(ii) Solute
(iii) Solvent
(iv) Suspension
(v) Solubility
(vi) Crystallization
(vii) Molarity (M)
(viii) Molality (m)
(ix) Mole fraction
(x) Dilute solution
(xi) Concentrated solution
(xii) Concentration
Solution: The homogenous mixture of two or more substances with uniform
composition is called solution. A solution has two components, solute and solvent.
Solute: The component of solution present in smaller amount is called solute.
Solvent: The component of solution present in greater amount is called solvent.
When water is solvent, the solution is called aqueous solution.
Suspension: A homogenous mixture that consists of visible particles, each of
which contains many thousands of molecules surrounded by molecules of liquid is
known as suspension.
Solubility: It is define as the amount of solute in gram dissolved at a given
temperature in 100 gm of the solvent.
Crystallization: The process in which dissolved solute comes out of solution
and forms crystals is called crystallization.
Molarity: It is define as the number of moles of the solute dissolved per dm3 or
1 litter of the solution. It is denoted by M.
Molality: It is define as the number of moles of the solute dissolved per kg or
1000 gm of the solvent. It is denoted by m.
Mole fraction: It is a unit of concentration, defined to be equal to the number
of moles of a component divided by the total number of moles of a solution.
Dilute Solution: The solution that contains less amount of solute as compared
to the amount of solvent is known as dilute solution.
Concentrated Solution: The solution that contain greater amount of solute
as compared to the amount of solvent is known as concentrated solution.
Concentration: In a solution, the amount of solute dissolved in a given quantity
of solvent is known as its concentration.
Colloid: A type of homogeneous mixture in which the dispersed particles do not
settle out.
Examples: Butter, Milk, smoke, fog, ink, paint
Specific gravity: It is the ratio of the density of a substance to the density of
water.
Example: The specific gravity of pure water at 4 °C is 1. Specific gravity is a unit value.
CHEMISTRY SOLUTION AND SUSPENSION CHAPTER IX SEVEN
38
Q - 2) Define Solubility and discuss the factors affecting Solubility:
It is define as the amount of solute in gram dissolved at a given temperature in 100 gram of the solvent. The following are the factors affecting solubility. i.e. (i)
Temperature (ii) Pressure (iii) Nature
(i) : If the temperature increases the solubility of solid increases
and the gases decreases in liquid.
Example: The solubility of sugar in water at 0 oC is 17.9g/100ml, whereas at 100 oC it is
48.7g/100ml.
When temperature increases the glass of cold water is warmed, bubble of air are seen
inside of the glass.
(ii) : The solubility of solids and liquids are not affected by pressure.
But the solubility of a gas in a liquid is directly proportional to the
pressure of gas, and this is called Henry’s Law.
Mathematically: 𝑚 ∝ 𝑝 or 𝑚 = 𝐾𝑝 (Where “m” is the amount of gas dissolved.)
Example:This effect uses in manufacture of bottled soft – drinks as Coca-Cola, 7 – up etc.
These are bottled under a CO2 pressure slightly greater than 1 atm. When bottle opens,
pressure decreases, so the solubility of CO2 also decreases, hence the bubbles of CO2 comes
out of solution.
(iii) : The solubility of solute and solvent may be polar
(H2O, Alcohol) and non – polar (Benzene, Carbon tetrachloride). Polar or Ionic solutes easily dissolve in polar solvents
Non – polar solutes easily dissolve in non – polar solvents.
Example: The common salt (NaCl) being ionic compound easily dissolve in polar
solvent like water (H2O). But it is insoluble in non – polar solvent like Benzene or Petrol. Q - 3) Define insoluble impurity and soluble impurity:
The impurity, which remains insoluble in the
solvent, is called insoluble impurity. The impurity, which remains in soluble at room
temperature, is called soluble impurity.
39
Q - 4) Define Saturated, Unsaturated and Super sturated solution: Saturated Solution:
The solution which contains maximum amount of solute in a gien solvent at a specific temperature and no more solute dissolve in it is called saturated solution. In this solution there is dynamic equlibiruim between dissolved and undessolved solute. Unsaturated Solution:
A solution in which the amount of the solute is less than it has the capacity to dissolve in large quantity of solvent is called unsaturated solution. Super Saturated Solution:
The solution which contains greater amount of dissolved solute than that are persent in a saturated solution. It is obtained by dissolving solute in saturated solution on heating. More solute would disssolve on heating saturated solution. Q - 5) Write differences between Solution and Suspenssion:
Difference Between Solution and Suspenssion
Solutions:
The size of particles is between 0.1 to 1 nm. Particles cannot be seen with low power microscope. It is homogeneous and transparent. Particles donot settle down. Components cannot be seprated by filtration. Suspenssion:
The size of particles is largeer than 1000 nm. Particles can be seen with low power microscope. It is hectrogeneous and opaque. Particles settle down. Components can be seprated by filtration.
40
Q - 6) Name the solute and solvent in the following solution:
a) Syrup b) Haze (dust in air)
c) Butter (water in fat) d) Fog
e) Gelies (water in fruit pulp) f) Smoke
g) Sodium h) Cheese (water in fat)
i) Foam (water in air) j) Mist
Answer: Solution Solute Solvents
a) Syrup Sucrose Water
b) Haze (dust in air) Dust Air
c) Butter (water in fat) Fats Water
d) Fog Water vapour Air
e) Gelies (water in fruit pulp) Air Water
f) Smoke Fruits pulp Water
g) Sodium Carbon particles Air
h) Cheese (water in fat) Mercury Sodium
i) Foam (water in air) Fats Water
j) Mist Water vapour Air
Q - 7) Explain why:
i. Common salt dissolves in water but not in petrol.
Ans: Common salt dissolves in water but not in petrol because like dissolve
like. Common salt being polar compound easily dissolves in polar solvent like
water but it is insoluble in non – polar solvent like petrol.
ii. Cold drinks are bottled under a CO2 pressure greater than 1 atm.
Ans: Cold drinks are bottled under a CO2 pressure greater than 1 atm because
when these bottled are opened, pressure decreases, so solubility of CO2 also
decreases, hence bubbles of CO2 come out of solution.
41
iii. 100 ml solution of KNO3 can not hold more than 37gm of KNO3 in
dissolved state.
Ans: 100 ml solution of KNO3 can not hold more than 37gm of KNO3 in dissolved state because this amount of KNO3 is required in making saturated solution. Q - 8) What do you mean by the percentage concentration and write some example of suspenssion in daily life.
Percentage Concentration: The percentage concentration is based on mass (M) and volume (V)
of the components solute and solvent in the solution.
It has four ways to express:
(i) Percentage in 𝑚
𝑚% (
𝑚𝑎𝑠𝑠
𝑚𝑎𝑠𝑠)%
(ii) Percentage in 𝑚
𝑣% (
𝑚𝑎𝑠𝑠
𝑣𝑜𝑙𝑢𝑚𝑒)%
(iii) Percentage in 𝑣
𝑚% (
𝑣𝑜𝑙𝑢𝑚𝑒
𝑚𝑎𝑠𝑠)%
(iv) Percentage in 𝑣
𝑣% (
𝑣𝑜𝑙𝑢𝑚𝑒
𝑣𝑜𝑢𝑚𝑒)%
Examples
(i) 05% (𝑚
𝑚) Solution means solute 5g in 95gm solvent.
(ii) 10% (𝑚
𝑣) Solution means solute 10g in solution 100cm3
(iii) 05% (𝑣
𝑚) Solution means solute 5 cm3 in solution 100g.
(iv) 15% (𝑣
𝑣) Solution means solute 15cm3 in solution 85cm3 solvent.
The examples of suspennsion in daily life:
i. Smoke A suspension of the particles of carbon in gas or air.
ii. Mud (smile) A Suspension of the particles of solid in small quantity of liquid.
iii. Foam (forth) A suspension of fine particles of a gas in a liquid.
iv. Emulsion A suspension of droplets of one liquid into another in which it is not soluble.
42
Q - 1) Define the following term: (i) Electrochemistry (ii) Electrolytes (iii) Non – Electrolytes (iv) Electrolysis (v) Electroplating (vi) Electrochemical equivalent (vii) Ampere (viii) Coulomb (ix) Faraday (x) Batteries
Electrochemistry: The branch of chemistry that deals with the relationship between
electricity and chemical reactions i.e. inter conversion of electric energy and chemical
energy is defines as Electrochemistry.
Electrolyte: The chemical compound, which conducts electricity in molten condition
or by its aqueous solution with chemical change, is called an Electrolyte. Examples: Hydrochloric acid (HCl), Sodium hydroxide (NaOH), Sodium Chloride (NaCl) etc.
Non - electrolytes: The compounds which do not conduct electricity in molten or in
aqueous solutions are called Non - electrolytes. Ex: Sugar, petrol, benzene etc.
Electrolysis: A process in which movements of the ions take place towards their
respective electrodes to undergo chemical changes under the influence of an applied
electric field is known as Electrolysis. Electroplating: The process of electrolysis that is used to coat one metal onto
another metal is known as Electroplating. It protects baser metal from corrosion and
makes them more attractive.
Electrochemical equivalent: The weight of substance deposited or liberated when
one coulomb of electric charge is passed through an electrolyte is known as
Electrochemical Equivalent. It is denoted by Z, and its SI unit is kg/coulomb.
Ampere: It is the basic unit of current that passes through a circuit for one second
that can liberate 0.001118g of Ag from silver nitrate (AgNO3) solution.
Coulomb: It is the basic unit of charge and is define as the quantity of charge when
one ampere of current is passed for one second.
C = Ampere (A) × time (s) Faraday: It is defining as the quantity of charge, which deposits or liberates exactly
one-gram equivalent of a substance. 1F = 96500 coulombs.
Batteries: The devices to produce electricity by the chemical reactions are known as
batteries. A battery is an assembly of two or more voltaic cells.
Electron affinity: It reflects the ability of an atom to accept an electron. The energy
change occurs when an electron is added to a gaseous atom. Atoms with stronger
effective nuclear charge have greater electron affinity.
Ex: H(g) + e- → H-(g); ΔH = -73 kJ/mol.
chemistry ELECTROCHEMISTRY
Chapter
IX EIGHT
43
Q - 2) State and explain Faradays first law of electrolysis:
:
It states that the amount of any substance deposited of
liberated at an electrode during electrolysis is directly proportional to the quantity of current passed through the electrolyte.
: If “w” is the weight or amount of a substance deposited or liberated
and “A” ampere of current is passed of “t” seconds, then according to the law:
w ∝ A × t w = Z ×A ×t
Where “𝑍” is a constant; known as electrochemical equivalent. Q - 3) State and explain Faradays Second law of electrolysis:
:
It states that the masses of different substances deposited or
liberated when same quantity of current is passed through different electrolytes, connected in series are proportional to their chemical equivalent masses.
: If we consider three different electrolytes, AgNO3, CuSO4 and Al(NO3)3
solutions, connected in series and same amount of current is passed through them.
Then the masses of Ag, Cu and Al deposited on their respective electrodes would be
directly proportional to their equivalent masses.
If 96500 coulombs of electric charge is passed then the masses of Ag, Cu and Al would
be 108g, 31.75g and 9g respectively.
Formula:
𝐸𝑞𝑢𝑖𝑣𝑎𝑙𝑒𝑛𝑡 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑎𝑛 𝑒𝑙𝑒𝑚𝑒𝑛𝑡 = 𝐴𝑡𝑜𝑚𝑖𝑐 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑒𝑙𝑒𝑚𝑒𝑛𝑡
𝑉𝑎𝑙𝑒𝑛𝑐𝑦 𝑜𝑓 𝑡ℎ𝑒 𝑒𝑙𝑒𝑚𝑒𝑛𝑡
Q - 4) Write down the relationship between equivalent mass and electrochemical equivalent:
If “e” is the gram equivalent mass and “Z” is Electrochemical Equivalent (E.C.E) then we can write it as:
𝑒 = 𝐹 × 𝑍
44
Q - 5) What do mean by Primary cell also describes the construction and working of Dry cell with diagram:
Primary Cell: The cell, which is used to convert chemical energy into electrical energy
and that, has irreversible characteristics, is known as Primary Cell or Dry Cell.
:
i. It has out zinc (Zn) vessel, which acts as anode, and
inert carbon (graphite) rod, which acts cathode.
ii. A mixture of manganese dioxide (MnO2) and carbon
powder surrounds the graphite rod.
iii. The electrolyte is a moist paste of ammonium
chloride (NH4Cl) and zinc chloride (ZnCl2).
iv. The upper top position is sealed with wax and a
copper cap is fitted on the top carbon rod to make
the electrical contact.
v. The whole cell is covered with a safety cover.
:
When a metallic wire Zn connects zinc and graphite
electrodes is oxidized to form Zn2+ ions, which pass
into the wet paste leaving behind electrons on the Zn
container the electrons, move from Zn electrode to
carbon electrode through the external circuit.
Q - 6) Describes the construction and working of Daniel cell with diagram:
Daniel Cell: It is the simplest of the Galvanic or Voltaic cell which is used to
convert chemical energy into electrical energy.
:
i. It consists of two half-cells, i.e. Zinc rod and Copper rod.
ii. Zinc rod is dipped in 1M ZnSO4 solution and Copper rod is dipped in 1M CuSO4
solution.
iii. The two half-cells electrodes are connected together to form a complete cell.
iv. A porous partition or a salt bridge separates the two half-cells.
v. The electrodes are connected externally through a volt Meter by metal wire.
45
:
When the connection are fully made. The cell starts producing electric current at once.
(i) Zn undergoes oxidation to form Zn2+ ions by the loss of 2e – two electrons to go into
ZnSO4. And acts as anode or negative electrode.
(ii) The electrons, which are free at Zn electrode, travel through the wire externally to
Cu electrode moreover accepted by CuSO4 solution.
(iii) Cu2+ ions undergo reduction to deposit copper metal at cu electrode, which acts as
cathode, or positive electrode.
(iv) In this process Zn – electrode dissolves in the solution of ZnSO4 and reduces in size,
while Cu – electrode grows in size due to the deposition of Cu – metal.
: 1.10 volt.
At Zn Electrode (Anode)
Zn(s) Zn2+(aq) + 2e–
At Cu Electrode (Cathode)
Cu(aq) + 2e– Cu(s)
Zn(s) + Cu2+ (aq) Zn2+ (aq) + Cu(s)
The Diagram Of Daniel Cell
VOLT METER
Zinc
Anode
SO42- Cu4
2-
SO42-
Copper
Cathode
Salt Bridge
ZnSO4 Solution CuSO4 Solution
Zn42-
46
Q - 7) What happens when electric current is passed through acidulated water? Give the reaction at two electrodes and mention the products at cathode and anode.
Ans: When electric current is passed through acidulated water it conducts electricity.
H2O(l)
H3O+(aq) + OH–(aq)
1. The (Hydronium) positive ions (H3O+) move towards cathode, gain electrons at
cathode and get neutralized to liberate H2 gas.
2. The (Hydroxide) negative ions (OH–) move towards anode, lose electrons at anode
and get neutralized to liberate O2 gas. The reaction at cathode:
H3O+
(aq) + 2e– H2 (g) + 2H2O(l)
The reaction at anode: 4OH –(aq) O2 (g) + 2H2O(l) + 4e–
The overall reaction: 2H2O(l) 2H2 (g) + O2 (g)
Result: It is observed that on electrolysis of water we get two volumes of hydrogen gas for
each volume of oxygen gas. Humphrey Davy who first did the electrolysis of water and
confirmed the formula of water is H2O.
Q - 8) Predict the net electrolysis reaction when molten NaCl is electrolyzed. Or describe the electrolysis of molten Sodium Chloride.
Ans: Sodium Chloride, NaCl (Salt) does not conduct electricity in the solid
state because its ions are held together tightly in a regular lattice
arrangements and cannot move but when it is electrolyzed or melted the
ions are freed from their lattice state and can move freely to conduct
electricity.
Procedure of Making Electrolyte: i. Some fused NaCl is taken in an electrolytic cell i.e. in a glass vessel.
ii. Two platinum rods (electrodes) are dipped into the fused salt (NaCl) and connected to the
battery outside the cell by wires.
iii. The battery has two terminal negative terminal as cathode and positive terminal as anode.
Acid
47
Working of the cell: When an electrical potential is passed through the Molten Sodium
Chloride (NaCl) salt, electrolysis starts.
i. The positive ions i.e. captions (Na+) are attracted towards cathode. ii. The negative ions i.e. anions (Cl–) are attracted towards anode. iii. At both electrodes, chemical reactions take place.
The reaction at cathode: Na+
(l) + e– Na(l)
The reaction at anode: 2Cl –(g) Cl2 (g) + 2e–
The overall reaction: 2Na+
(l) + 2Cl–(l) 2Na (l) + Cl2 (g)
Result: It is observed that on electrolysis of molten Sodium Chloride (NaCl) we get sodium
metal (Na) at cathode and Cl2 gas is liberated at anode.
Q - 9) Difference between Primary cell and Secondary cell. Primary Cell: i. It is used to convert chemical energy into electrical energy and it has dense material.
ii. It becomes dead after sometimes and cannot be reused. (But nowadays possible)
iii. Example Dry Cell and mercury cell.
Secondary Cell: i. It is also used to convert chemical energy into electrical energy that has liquid material.
ii. It can be reused over and again by recharging.
iii. Example Lead Storage battery and nickel – cadmium storage cell.
Battery
Cl – Na+
Anode (+) Cathode (–)
48
Q - 10) Describe the process of nickel plating. Nickel Plating:
The process of dropping a thin layer of nickel metal over anther metal object with the help of electrolysis is called nickel plating. Procedure:
i. A cell for electroplating of nickel consists of a piece of pure nickel as anode and the spoon
or any other object as cathode.
ii. A solution of nickel Sulphate (NiSO4) is used as the electrolyte in the electrolytic cell.
iii. In addition, both electrodes (anode and cathode) join externally with a battery.
iv. On passing electric current, the anode (Ni) dissolves in the solution and forms Ni2+ ions.
v. Then Ni2+ ions from the solution move towards cathode. They gain electrons and reduce to
Ni metal on the surface of spoon (cathode).
The reaction at cathode: Ni2+
(aq) + 2e– Ni(s)
The reaction at anode: Ni(s) Ni2+
(aq) + 2e–
The overall reaction:
Ni (s) Ni(s)
Result: It is observed that the net reaction is simply the transfer of Ni as Ni2+ through NiSO4
solution towards the cathode i.e. spoon and get it coated with Ni metal on the surface. Q - 11) Describe the process of Chromium plating. Chromium Plating:
The process of dropping a thin layer of chromium metal over anther metal object with the help of electrolysis is called chromium plating. Procedure:
i. A cell for electroplating of chromium consists of a piece of pure chromium as anode and the
spoon or any other object as cathode.
ii. A solution of chromium Sulphate Cr2 (SO4)3 is used as the electrolyte in the electrolytic cell.
iii. In addition, both electrodes (anode and cathode) join externally with a battery.
iv. On passing electric current, the anode (Cr) dissolves in the solution and forms Cr3+ ions.
v. Then Cr3+ ions from the solution move towards cathode. They gain electrons and reduce to
Cr metal on the surface of spoon (cathode).
The reaction at cathode: Cr3+
(aq) + 3e– Cr(s)
The reaction at anode: Cr(s) Cr3+
(aq) + 3e–
The overall reaction:
Cr (s) Cr (s)
Result: It is observed that the net reaction is simply the transfer of Cr as Cr3+ through Cr2(SO4)3
solution towards cathode i.e. spoon and get it coated with Cr metal on the surface.
49
Q - 12) What is the function of salt bridge or porous partition in an electrochemical cell? Function of salt bridge: The function of salt bridge or porous partition in electrochemical cell is to prevent the mixing of two solutions and it allows ions to move through one part to another. Q - 13) Predict what would be formed (i) at the anode and (ii) at the cathode when each of the following molten salts is electrolyzed using inert electrodes.
a) NaCl b) MgBr2 c) CaCl2
Salts At cathode At anode
a) NaCl Na (l) Cl2
b) MgBr2 Mg (l) Br2
c) CaCl2 Ca (l) Cl2
Q - 14) Write down the uses of electrolysis. Uses of electrolysis:
I. It is used for the extraction of certain metals from their ores.
II. It is also used in electroplating of metal.
III. It is also used to purify many metals Q - 15) Define electrochemical cell. Electrochemical cell: The cell, which is used to convert chemical energy into electrical energy, is called
electrochemical cell and it is generally known as Galvanic or Voltaic cell.
Examples:
The simplest of the Galvanic or Voltaic cells is Daniel cell. Q - 16) Which of the following pairs of terms have the same meanings and which have different meanings?
(i) Voltaic cell and Galvanic cell. (ii) Cell and battery
(iii) Electrolytic cell and electrochemical cell
Ans: The pair of Voltaic and Galvanic cell has the same meanings because two
pioneers in electricity Luigi Galvani and Alexandra Volta exposed it. The other two pairs are different in meanings because they have different properties and processing procedures.
50
Q - 1) Define the following term:
1) Salt
2) pH
3) Hydrolysis
4) Titration
5) Neutralization
6) Basicity of Acid
7) Double salts
8) Standard solution
9) Acidity of base
Salt: A salt is ionic compound produced when a base neutralizes an acid. Example NaCl, KNO3.
pH: It is define as the negative logarithm of the hydrogen ion H+ or H3O+ ions
concentration in moles per litter.
Hydrolysis: The complete dissociation of salt into acid or base in aqueous
solution is known as hydrolysis.
Titration: It is the chemical process by which, we can determine the concentration of unknown solution.
Neutralization: A reaction in which an acid and a base form an ionic compound (salt and water) is called neutralization.
Basicity of acid: The number of replaceable or ionize hydrogen (H+) ions present
in molecule of an acid is called basicity of acid. Double salts: The crystalline compounds, which are obtained when two specific
salts are crystallized together, are known as double salts. Standard solution: The solution whose concentration is known is called standard
solution. Acidity of base: The number of replaceable or ionize hydroxide ions (OH–) present
in molecule of base is called acidity of base. Q - 2) Write down the importance of pH. Importance of pH:
I. pH plays great role in the field of Biology. II. It is also important for water treatment and food processing.
III. It also plays an important role in corrosion control and soil conditioning. IV. It has some important in the process of electroplating.
The pH values of several biological fluids.
Lemon juice 2.3 Human blood 7.35 – 7.45 Vinegar 2.8 Cow’s milk 6.5
Tomato juice 4.2 Human urine 5.0 – 7.0 Salvia 7.0 Egg white 7.8
chemistry ACIDS BASES AND SALTS
Chapter
IX NINTH
51
Q - 3) State Bronsted Lowry theory of acids and bases and explain it with example of HCl and NH3.
:
“He states that an acid is a substance having a tendency to donate one or more protons while base is substance having a tendency to accept (add) protons.” Bronsted – Lowry acid = A substance that can donate (H+). Bronsted – Lowry base = A substance that can accept (H+).
: Lowry takes hydrochloric acid (HCl) and water (H2O) is protons donors and
act as Bronsted-Lowry acids whereas (H2O) and ammonia (NH3) are protons acceptors
and are known as Bronsted Lowry bases.
52
Q - 4) State Lewis concept of acids and bases and explain it with example:
:
He states that an acid is any species (molecules or ions) which
can accept a pair of electrons, and base is any species that can donate a pair of electrons. Lewis acid = An electron pair acceptor. Lewis base = An electron pair donor.
: When ammonia (NH3) reacts with proton (H+) to form ammonium ion (NH4
+) in which
the Nitrogen of NH3 donates a pair of electrons whereas the (H+) accepts that pair of
electrons for bond formation.
Q - 5) What is Arrhenius theory of acid and bases why is the Arrhenius theory not satisfactory for acids and bases:
:
He states that an acid is any substance that yields hydrogen ions
(H+) in water and a base is a substance that yields hydroxide ions (OH–) in water.
Arrhenius acid = HCl and H2SO4 HCl(aq) H+(aq) + Cl–(aq)
Arrhenius base = NaOH and KOH
NaOH(aq) Na+(aq) + OH–
(aq)
His theory does not satisfy for acids and bases because they apply only to water
solution and it does not account for the basicity of ammonia (NH3) that doesn’t
contain (OH) group.
53
Q - 6) Write down the physical and chemical properties of Acids and Bases: Acid is a substance that gives H+ or H3O+ in aqueous solution.
Base is a substance that gives OH – or in aqueous solution.
: : 1. They have a sour taste.
2. Change the color of litmus form blue to red.
3. Strong acids can harm human, things etc.
4. They conduct electricity in aqueous
solution.
1. They have bitter taste.
2. Change the color of litmus from red to blue.
3. They have slippery touch.
4. They also conduct electricity in aqueous
solution.
: 1. When acids react with metals like (Zn, Mg and Fe) they produce H2 gas and salts.
Zn(s) + 2HCl(aq) ZnCl2(s) + H2(g)
Mg(s) + 2HCl(aq) MgCl2(s) + H2(g)
2. When acids react with carbonate and bicarbonates they produce CO2 gas.
CaCO3(s) + 2HCl(aq) CaCl2(aq)+ H2O(l) + CO2(g)
NaHCO3(s)+ HCl(aq) NaCl(aq) + H2O(l) + CO2(g)
3. When acids react with oxides and hydroxides of metals they produce salts and water.
FeO(s) + 2HCl(aq) FeCl2(aq) + H2O(l)
Fe(OH)3(s)+ 3HCl(aq) FeCl3(aq) + 3H2O(l)
4. When acids react with bases they produce salts and water.
NaOH(aq) + 2HCl(aq) NaCl(s) + H2O(l)
Ca(OH)2 + 2HCl(aq) CaCl2(s) + H2O(l)
:
1. Bases react with fats to form soap.
2. When bases react with metals or non-metals they dissolve them and produce H2 gas.
2Al + 2NaOH(aq) + 2H2O(l) 2NaAlO2 + 3H2
3. When bases react with acid they produce water and salts.
NaOH(aq) + 2HCl(aq) NaCl(s) + H2O(l)
Ca(OH)2 + 2HCl(aq) CaCl2(s) + H2O(l)
4. When bases react with heavy metal salts they form their salt solutions.
3NaOH + FeCl3 Fe(OH)3 + 3NaCl
2NaOH + MgCl2 Mg(OH)2 + 2NaCl
54
Q - 7) What is salt and explain its four examples:
Salt: A salt is ionic compound produced when an acid is neutralized by a base.
For example sodium hydroxide (NaOH) neutralizes hydrochloric acid (HCl) to form sodium
chloride (NaCl) and water (H2O).
NaOH(aq) + 2HCl(aq) NaCl(s) + H2O(l)
There are four kinds of salts as following:
(i) Normal Salt (ii) Acidic Salt (iii) Basic Salts (iv) Double Salt
(i) Normal Salt: Salts which are formed by the complete neutralization of an acid by a base e.g. (NaCl, NaNO3, K2SO4) etc. are known as normal salts and these do not have replaceable hydrogen ions (H+) or hydroxyl groups (OH–).
(ii) Acidic Salt: Salts, which are formed by the partial neutralization of an acid by a base e.g.
(KHCO3, NaHSO4) etc. are known as acidic salts and these, have replaceable hydrogen atoms (H+).
NaOH(aq) + H2SO4(aq) NaHSO4(s) + H2O(l)
(iii) Basic Salt: Salts which are formed by the partial neutralization of an base by an acid e.g.
Mg(OH)Cl, Zn(OH)Cl etc. are known as basic salts and these have replaceable (OH–) hydroxyl groups.
Mg(OH)2(aq) + HCl(aq) Mg(OH)Cl(s) + H2O(l)
(iv) Double Salt: The crystalline compound which are obtained, when two specific salts are
crystallized together are called double salts. These have definite chemical composition. Such as
(i) Potash Alum K2SO4 Al2(SO4)3 24H2O (ii) Mohr’s Salt FeSO4 (NH4)2 SO4
(iii) Chrome Alum K2SO4 Cr2(SO4)3 24H2O (iv) Carnalities KCl MgCl26H2O
Q - 8) What is chemical reaction define and give one example each of the following (i) Neutralization (ii) Hydrolysis Chemical Reaction: The process in which chemical change in the nature and composition of some substance occurs is called a chemical reaction. Neutralization: The process in which two reactants acid and base reacts with each other to form salt and water is called neutralization.
NaOH(aq) + 2HCl(aq) NaCl(s) + H2O(l) Hydrolysis: The process in which acid or base reacts with water to form either weak acid and strong base or strong acid and weak base is called hydrolysis.
FeCl3 + 3H2O Fe(OH)3 (Weak Base) + 3HCl (Strong Acid)
Na2CO3 + 2H2O 2NaOH (strong Base) + H2CO3 (Weak Acid)
55
Q - 9) Explain with illustration that what are strong acid and base and weak acid and base. Also write formulas of them: Strong Acid: An acid that produces large number of H+ ions in aqueous solution is
said to be a strong acid and it is almost completely dissociated.
Weak Acid: An acid that produces small number of H+ ions in aqueous solution is
said to be a strong acid it is only partially dissociated.
Strong Base: A base that produces large number of OH– ions in aqueous solution is
said to be a strong acid and it is almost completely dissociated.
Weak Base: A base that produces small number of OH– ions in aqueous solution is
said to be a strong acid it is only partially dissociated.
Formulas of acid and bases Strong acid Strong base
Hydrochloric Acid HCl Sodium Hydroxide NaOH
Nitric Acid HNO3 Potassium Hydroxide KOH
Sulphuric Acid H2SO4 Barium Hydroxide Ba(OH)2
Weak acid Nitrous Acid HNO2 Carbonic Acid H2CO3
Phosphoric Acid H3PO4 Acetic Acid CH3 – COOH
Hydro fluoric Acid HF Formic Acid HCOOH
Weak base
Ammonium Hydroxide NH4OH
Magnesium Hydroxide Mg(OH)2
Beryllium Hydroxide Ba(OH)2
Q - 10) Sulphuric acid (H2SO4) is strong acid. H2SO4- is weak acid
account for the difference in strength: H2SO4:
H2SO4 is strong acid because it ionizes completely in aqueous solution and produces two H+ ions. While
HSO4–:
HSO4– is weak acid because it ionizes partially in aqueous solution and
produces only one H+ ion. Q - 11) Give an example of mono-parotic, di-parotic and tri-parotic acid:
Mono-practice acid = HCl Di-parotic acid = H2SO4 Tri-parotic acid = H3PO3
56
Q - 12) Define acidic, basic and neutral solutions in terms of H+ ion concentration. Indicate whether each of the following solution will be acidic, basic or neutral:
a) Strong acid and strong base Ans: Neutral solution b) Strong acid and weak base Ans: Acidic solution c) Weak acid and strong base Ans: Basic solution
Acidic solutions: It is the solution in which number of hydrogen ions (H+) increase is said to be acidic solution. Basic solutions: It is the solution in which number of Hydroxide ions (OH–) increase is said to be basic solution. Neutral solutions: The solution in which number of hydrogen ions (H+) and hydroxide ions (OH–) become equal is said to be Neutral solution. Q - 13) Define molarity. What is molar solution? Molarity: It is defined as the number of moles of solute dissolved per 1 litter or 1dm3 solutions of a solution and denoted by M. Molar solutions: The solution which contains 1 mole of solute in 1dm3 (1liter) of solution is known as molar solution.
Q - 14) Define term Amphoteric and give example? Amphoteric: A substance (such as water) that can behave as both acid and base is said to be an amphoteric substance. Example:
HCl(aq) (Acid) + H2O(l) (Base) H3O+(aq) (Acid) + Cl–(aq) (Base)
H2O(l) (Acid) + NH3(aq) (Base) NH4(aq) (Acid) +OH–(aq) (Base)
Q - 15) Give an equation to show the dissociation of water? Dissociation of water equation: A proton from one water molecule is transferred to another water molecule, leaving behind (OH–) ion and forming H3O+ ion.
𝑀 =𝑚
𝐹𝑀×1000
𝑣
57
Q - 16) Define pH? Explain why a natural solution is said to have a pH of 7? pH: 1. It is defined as the negative logarithm of hydrogen ion (H+) or (H3O+)
concentration in mole per litter. 2. A natural solution is said to have a pH of 7 because in any natural
solution the H+ ions concentration is 1 × 10−7 M, having pH of 7. Mathematically: Titration results by pH
pH = − logH+
pH = − log 10−7
pH = −(−7) pH = 7
Indicator Colour in acid pH – range Color in base
Methyl orange Red 3 – 5 Yellow
Litmus Red 6 – 8 Blue
Phenolphthalein Colorless 8 – 10 Pink (Red)
Q - 17) Describe the commercial preparation and uses of salts? 1. Commercial Preparation of SODIUM CARBONATE:
(Na2CO3.10H2O) (Na2CO3) Sodium carbonate is commercially prepared by “Solvay process” or Ammonia soda process. The raw materials are limestone (CaCO3), sodium chloride (NaCl) and ammonia (NH3) and water (H2O).
Step of process
(i) Lime stone is heated to yield calcium oxide (CaO) and the CO2 gas. (ii) This CO2 is passed into aqueous solution of ammonia, and the ammonium
bicarbonate (NH4HCO3) is produced. (iii) This (NH4HCO3) reacts with aqueous cold solution of NaCl at 15 0C, called Brine
to yield (NH4HCO3) which is not soluble at low temperature 15 0C and this precipitates out.
(iv) This (NaHCO3) on heating yields sodium carbonate (Na2CO3). Anhydrous sodium carbonate (Na2CO3) is known as soda – ash and sodium carbonate dehydrate (Na2CO3 10H2O) is commonly known as washing soda.
Chemical equations H
CaCO3 (s) CO(s) + CO2(g)
NH3(g) + CO2 (g) + H2O(l) NH4HCO3(aq) At 15 0C brine
NH4+HCO3
– (aq) + Na+Cl– NH4
+Cl–(aq) + NaHCO3(s) H
2NaHCO3(s) Na2CO3(s) + H2O(l) + CO(g)
58
Uses of sodium carbonate (Na2CO3) (i) It is used in the softening of water. Sodium carbonate finishes carbonate ion
to precipitate calcium and magnesium ions. (ii) It is used as cleaning agent and in making of soap. Detergents and paper. (iii) It is used in making ordinary glass (Na2SiO3), which is used in bottles. 2. Commercial preparation of Sodium hydrogen Carbonate:
(NaHCO3) (Baking Soda) “Solvay Process” forms (NaHCO3) sodium hydrogen carbonate or baking soda but mostly it is prepared by passing the stream of CO2 through concentrated aqueous Na2CO3 solution.
Na2CO3 (s) + CO2(g) + H2O(l) 2NaHCO3 (s)
Uses of sodium hydrogen carbonate (NaHCO3) (i) It is used in the preparation of baking powder. (ii) It is also used in the preparation of effervescent drinks and fruit salts. (iii) It is also used in medicines to remove acidity of stomach (i.e. as Antacid) (iv) It is also used in fire extinguishers. 3. Commercial preparation of Copper Sulphate: (CuSO45H2O) (Blue
Vitriol) (CuSO4) copper Sulphate or cupric Sulphate, which is also known as blue vitriol, or blue stone. (i) Reacting copper scraps with dilute Sulphuric acid in the presence of
air prepare it. 2Cu (s) + 2H2SO4(aq) + O2 2CuSO4 (aq) + 2H2O
(ii) It can be also prepared by the treatment of CuO or CuCO2 with dilute Sulphuric acid (H2SO4).
CuO + H2SO4(aq) (dilute) CuSO4 + H2O
CuCO3 + H2SO4(aq) (dilute) CuSO4 + H2O + CO2
Uses of sodium hydrogen carbonate (NaHCO3) (i) It is used in textile (mordant), tanning, electric batteries, hair dyes and
in electroplating. (ii) It is used as germicide, insecticide, preservative for wood, paper pulp. (iii) It is used in calico printing, making synthetic rubber and copper salts
e.g. steels, green paint. (iv) It is used in paint and varnish industries. (v) It is also used to kill fungus and moulds.
59
4. Commercial preparation of Magnesium Sulphate: (MgSO47H2O)
(Epsom - Salts) (MgSO4) Magnesium Sulphate is also known as “Epsom Salts”. (i) It is prepared by reacting H2SO4 with magnetite (MgCO3).
MgCO3 (magnesite) + H2SO4(aq) MgSO4 + 2H2O + CO2
(ii) It is also prepared by reacting H2SO4 with dolomite (MgCO3 CaCO3).
MgCO3 CaCO3 (dolomite) + 2H2SO4(aq) MgSO4 + CaSO4+ 2H2O + CO2
(iii) It is nowadays prepared by heating kieserite (MgSO4H2O) under pressure with water (H2O). MgSO4 H2O (kieserite) + 6H2O MgSO4 7H2O (Epsom salt)
Uses of magnesium Sulphate (MgSO47H2O) (i) It is used as a mild purgative in medicines. (ii) It is used in dying and tanning process. (iii) It is used in fire proof fabrics. (iv) It is used in paper industry. (v) It is used in manufacture of ceramics, glazed tiles and match boxes. 5. Commercial preparation of Potash Alum: (K2SO4Al2SO424H2O)
(Ordinary Alum) Potash Alum is known as ordinary salts. It is prepared by reacting K2SO4 and Al2SO4with water. When equ – molecular quantities of K2SO4 and Al2SO4 are dissolved in water and the solution is allowed to evaporate. Crystals of K2SO4 Al2SO4 24H2O which is called Ordinary Alum or Potash Alum are separated out.
K2SO4 + Al2SO4 + 12H2O K2SO4 Al2SO4 24H2O
Uses of potash alum (K2SO4 Al2SO4 24H2O) (i) It is used as antiseptic and as a mouth wash. (ii) It is used in sizing paper and tanning leather. (iii) It is used in purifying water. (iv) It is used in dying as mordant to fix insoluble dye to fiber. (v) It is used in medicine.
Q - 18) Define acid – base titration, standard solution and equivalence point? Standard Solution: A solution whose molarity or strength is known is called standard solution.
60
Acid – Base Titration: In Acid – Base titration, a solution of known concentration (base) is added gradually to a solution of unknown concentration (acid) so as to determine the concentration of unknown solution. Equivalence point or End Point: The point at which reaction is completed is called the end point. At this point acids and base becomes equivalent to neutralize each other. This point is also known as the Equivalence Point. Q - 19) Identify the following as a weak or strong acids or bases?
(i) NH3 (ii) H3PO4 (iii) LiOH (iv) HCOOH (Formic acid)
(v) H2SO4 (vi) H2CO3 (vii) Ba(OH)2
Answer: Strong Acid: Strong Base
H2SO4 Ba(OH)2
Weak Base Weak Acid
LiOH, NH3 H2CO3 , H3PO4, HCOOH (Formic acid)
Q - 20) Describe clearly how a solution of HCl could be titrated with a solution of NaOH?
Step of Titration:
i. Fill the burette with the given solution of NaOH. Read and record the initial reading then let
the burette drain into beaker down to the zero mark before using it.
ii. Pipette out 10cm3 of HCl in a conical flask.
iii. Add one or two drops of phenolphthalein indicator.
iv. Add slowly the NaOH solution, from the burette into the conical flask with constant shaking.
v. Stop adding the NaOH solution when the mixture in the titration flask becomes light pink.
vi. Record the final burette reading.
vii. Take more readings by repeating experiment in same manner.
Information required for calculation of titration:
The following information is required for calculation of titration.
i. The volumes of the solution of acids or base must be known.
ii. The concentration of one of the solution also must be known.
iii. The balanced chemical equation for the reaction.
61
Q - 1) Define the following term: 1. Heat content
(Enthalpy)
2. Heat of Neutralization
3. Thermochemistry
4. Exothermic reaction
5. Endothermic reaction
Heat content (Enthalpy): The energy given out or absorbed at constant pressure is
called enthalpy. It is denoted by H.
Heat of Neutralization: The amount of heat released during a neutralization reaction
in which 1 mole of water is formed is called as the heat of neutralization.
Thermochemistry: The branch of chemistry that deals with the study of heat changes in
chemical reactions is called Thermochemistry.
Exothermic reaction: It is the chemical change during which heat is given out or
released. It is denoted by –H.
Endothermic reaction: It is the chemical change during which, heat is taken in or
absorbed. It is denoted by +H.
Q - 2) Define a thermochemical reaction. What is meant by enthalpy of a reaction? Also Define Exothermic reaction with two examples: Thermochemical reaction: The chemical reactions during which material changes are accompanied with change in heat energy are called Thermochemical Reaction. Enthalpy: The heat given out or absorbed at constant pressure is called enthalpy. It
is denoted by H. Exothermic reaction: The chemical change in which heat is given out or released is known as
exothermic reaction. It is denoted by –H. Example of exothermic reaction: i. The combustion of coal in air is the example of exothermic reaction.
393.7 kilo Jules per mole of heat energy is released when 1 mole of coal is burnt in 1 mole of O2 to produced 1 mole of CO2.
C(s) + O2 (g) CO2(g) – H = -393.7 kj/mol
ii. Burning of methane in presence of oxygen is 2nd example of exothermic reaction.
CH4(s) + 2O2 (g) CO2(g) + 2H2O – H = -890 kj/mol
chemistry CHEMICAL ENRGETICS
Chapter
IX ten
62
Q - 3) Define Endothermic reaction and also give two examples Endothermic Reaction?
Endothermic reaction:
The chemical change in which heat is taken in or absorbed is known as
endothermic reaction. It is denoted by +H.
Example of endothermic reaction:
i. The decomposition of water into Hydrogen and Oxygen is the example of endothermic reaction. 286 kilo Jules/mole of heat energy is absorbed when 1 mole of H and ½ mole of O decomposed.
H2O(l) H2(g) + ½ O2 (g) + H = +286 kj/mol
ii. Combination of Nitrogen (N) and Oxygen (O) is 2nd example of endothermic reaction.
½N2(g) + ½O2 (g) NO (g) + H = +90.25 kj/mol Q - 4) Define Heat of Neutralization: what would be the value of reaction of neutralization when strong acid reacts with strong base?
Heat of Neutralization:
The amount of heat released during a neutralization reaction in which one
mole of water (H2O) formed; is called as the Heat of neutralization.
The value of reaction of neutralization would be almost same when
strong acid react with strong base.
Q - 2) How is food warm by exothermic reaction?
Warming Food by exothermic reaction:
The pouch that contains the food attached to flameless radiation heater.
The heater contains chemicals that react with water to produce heat.
When the pouch placed in a bad and water added temperature of the food
reaches to 60 0C in about 15 minutes.
Mg(s) + 2H2O(l) Mg(OH)2(s) + H2 (g) H = –3.53 kj/mol
THE END OF FIRST BOOK PART 1
