acid base and salt
TRANSCRIPT
ACID BASE AND SALT
TUSHAR BHARDWAJ Page 1 9810445195, 7503684851
TOPICS
1. INTRODUCTION OF ACIDS
2. TYPES OF ACIDS AND THEIR PROPERTIES
3. USES OF ACIDS
4. INTRODUCTION OF BASES
5. TYPES OF BASES AND THEIR PROPERTIES
6. USES OF BASES
7. PH SCALE AND USES IN EVERY DAY LIFE
8. INTRODUCTION OF SALTS
9. SOME IMPORTANT SALTS AND THEIR FORMATION AND
USES
10. HYDRATED & ANHYDROUS SALTS
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ACIDS
Acids are those substances which ionize on dissolving in water to produce
hydrogen ions. Such as: HCl, H2SO4, HNO3, H2SO3 etc.
HCl H+ + Cl-
H+ + H2O H3O+
HNO3 H+ + NO3-
H+ + H2O H3O+
(HYDRNIUM ION)
TYPES OF ACIDS ON THE BASIS OF THEIR OCCURRENCE
a) Mineral acids
Those acids that are prepared from minerals of earth are called Mineral
acid. Such as: HCl, H2CO3, H2SO4, HNO3etc.
b) Organic acids
Those acids which present in plant and animal body are called Organic
acid. These are natural and weak acids. Such as: Citric acid (Lemon),
lactic acid (Curd), Acetic acid (Vinegar), Methanoic acid (Ant sting).
TYPES OF ACIDS ON THE BASIS OF THEIR POWER
a) Those acids which are completely ionize in water and produces a large
number of hydrogen ions are called Strong acid. Such as:
H2SO4 H+ + SO42-
b) Acids which are partially ionized in water and thus produces a small
amount of hydrogen ions is called Weak acids. Such as:
CH3COOH CH3COO- + H+
PROPERTIES OF ACIDS
a) Acids have sour taste.
b) Acids turn blue litmus to red.
c) Acid conduct electricity.
d) Acid react with metal to form hydrogen gas.
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Zn + H2SO4 ZnSO4 + H2
Hydrogen gases on burning create the pop sound.
Curd and other food stuffs should not be kept in metal vessels.
e) Acid react with the metal carbonate to form CO2.
Na2CO3 + HCl NaCl + CO2+ H2O
NaHCO3 + HCl NaCl + CO2 + H2O
When we pass CO2 through the lime water it turns milky due to the
formation of CaCO3.
Ca(OH)2 + CO2 CaCO3 + H2O
If excess of CO2 gas is passed through the lime water then white ppt
dissolve and clear again.
CaCO3 + CO2 + H2O Ca(HCO3)2
(Insoluble salt) (Soluble salt)
f) Acids react with the bases to form salt and water this reaction is called
the Neutralization reaction.
NaOH + HCl NaCl + H2O
g) Acid react with the metal oxide to form salt and water.
CuO + HCl CuCl2 + H2O
(Black) (Blue green)
h) Acids have corrosive nature
Mineral acids cause the severe burn on the skin and eat up
materials like cloth, wood, metal structure and stone. So they
called as corrosive in nature.
Strong bases such as NaOH are also very corrosive in nature.
i) Acids do not show acidic behavior in the absence of water.
HCl gas does not change dry blue litmus paper because it has no
hydrogen ions in it.
j) Acids are ionic compound so conduct the electricity.
USES OF MINERAL ACID
a) Nitric acid is used for making fertilizers, explosives (Tri Nitro Toluene),
dyes and plastics.
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b) Sulphuric acid is used in manufacture of fertilizers {(NH4)2SO4},
explosive, car battery etc.
c) HCl is used for removing oxide film from steel object and for removing
‘Scale’ deposit from inside the boilers.
BASES Those substances which dissolve in water to produce hydroxide ion in
solution are called bases.
NaOH Na+ + OH-
Mg(OH)2 Mg2+ + OH-
TYPES OF BASES
A base which completely ionises in water and thus produces a large
amount of hydroxide ions is called strong base. Such as: NaOH, KOH etc.
A base which is partially ionised in water and thus produces a small
amount hydroxide ions is called weak base. Such as : NH4OH, (CaOH2)
ALKALIS
A base which dissolves in water is called an alkali. Such as: NaOH, KOH,
Ca(OH)2, NH4OH, Mg(OH)2.
PROPERTIES OF BASES
a) Bases have bitter taste.
b) Bases feel soapy to touch.
c) Bases turn red litmus to blue litmus.
d) Bases conduct electricity.
e) Bases react with some metals to form hydrogen gas.
NaOH + Zn Na2ZnO2
f) Bases react with acids to form salt and water.
NaOH + H2SO4 Na2SO4 + H2O
g) Bases react with non-metal oxide to form salt and water.
CO2 + Ca(OH)2 CaCO3
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Non metal oxides are acidic in nature.
USES OF BASES
Sodium hydroxide is used in the manufacture of soap, paper and
rayon.
Calcium hydroxide is used in manufacture of bleaching powder.
Sodium carbonate is used as washing soda and for softening of
hard water.
Sodium hydrogen carbonate is used as baking soda in cooking.
Magnesium hydroxide is used as an antacid to neutralize excess
acid in the stomach.
PH SCALE
In 1909 Sorenson devised a scale on which the strength of acidic solution as
well as basic solutions could be represented by use of the hydrogen ion
concentration in them.
PH of a solution is inversely proportional to the concentration of H+ in
it.
PH α 1/[H+]
It has value from 0 to 14
Dark red Green Violet
0 7 14
Increasing acidic character Increasing basic character
PH is called universal indicator. It is a mixture of different indicators
which give different color at different PH values of entire PH scale.
It is used to measure the value of PH of solution.
IMPORTANCE OF PH IN DAILY LIFE
A) SELF DEFENSE BY ANIMALS AND PLANTS
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Many animals and plants protect themselves from their enemies by
injecting painful and irritating acids and bases into their skin. Such as:
Honey bee stings a persons, it inject an acidic liquid into the skin that
causes immense pain and irritation. Then by rubbing mild base like
baking soda on stung area of skin gives reliefs.
When a person happens to touch the leaves of nettle plant accidently,
the stinging hair of nettle leaves inject the Methanoic acid into the skin
of the person causing burning pain.
B) ROLE OF PH IN OUR DIGESTIVE SYSTEM
Our stomach produces HCl (1.4 PH). This help in our food digestion
without harming the stomach. Sometime excess of it produced that
causes indigestion and results pain and irritation, at this Mg(OH)2 AND
NaHCO3 are used to cure it.
C) PH CHANGE AS THE CAUSE OF TOOTH DECAY
When we eat sugary food, bacteria present in our mouth break down
the sugar to form acids. This acid lowers the pH in the mouth. Tooth
decay start when the pH of mouth falls below 5.5 at this acid become
strong and act on enamel of our teeth and start to corrode it. Regular
cleaning is the best method to prevent it.
D) SENSITIVITY OF PLANTS AND ANIMALS TO PH CHANGE
Most of plants grow best when the PH of soil is close to the 7. If the soil
is too acidic or too basic, plants does not grow. In acidic condition we
can treat with CaO, Ca(OH)2 or chalk hence excess acid is to neutralize.
Our body work well within a narrow PH range of 7.0 to 7.8. Aquatic
animals can survive in narrow range of PH change.
When pH of rain water is about 5.6.It is called acid rain. Too much acid
rain can cause lower the PH of river water.
INDICATOR
An indicator is a dye that changes colour when it is put into an acid or a base.
It tells us the nature of testing substances that it is acid or base, by notice the
change in its colour.
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There are three common indicators to test for acids and bases.
A) METHYL ORANGE
Orange ACID Red
Orange BASE Yellow
B) PHENOPTHELENE
Colorless ACID Colorless
Colorless BASE Pink
C) LITMUS (NATURAL INDICATOR)
Litmus extracted from lichen plant. It may be in the paper form or
solution.
Purple ACID Red
(solution)
Purple BASE Blue
(solution)
Litmus paper ACID Red
(Blue)
Litmus paper BASE Blue
(Red)
D) OLFACTORY INDICATOR
Those substance whose smell changes in acidic or basic solutions. It is
of two types:
Onion
Onion treated cloth ACID can detect smell
Onion treated cloth BASE cannot detect smell
Vanilla
Vanilla ACID can detect smell
Vanilla BASE cannot detect smell
SALT
Salt is a compound formed from an acid by replacement of the hydrogen in
the acid by metal.
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It is formed when acid react with base.
First part of salt comes from base and second part from acid.
KOH (base) + HCl (acid)
KCl(salt)
Nature of salt depends on the nature of acid and base that take
part to form salt. If both are strong or both are weak then
obtained salt will be neutral (7). If one if is strong and other is
weak then name of strong will be given to salt.
COMMON SALT
The chemical name of common salt is sodium chloride (NaCl).
NaOH + HCl NaCl + H2O
Common salt occurs naturally in the sea water and as rock salt.
Major salt present in sea water is the common salt. It is obtained
from sea water by the process of evaporation. While the Rock salt
is mined from underground deposits just like coal.
USES OF COMMON SALT
a) It is used as raw materials for HCl, Na2CO3, NaHCO3etc
b) It is used for cooking and improves flavour.
c) It is required for proper working of nervous system.
d) It is used for the manufacture of soap and help to melt ice during
winter in areas where snow depositson road.
e) It is used in pickles and for curing meat.
SODIUM HYDROXIDE
It is commonly called Caustic soda. The chemical formula is NaOH.
PRODUCTION
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NaCl + H2O ELECTRICITY NaOH + Cl2 + H2
(Brine) (Caustic soda)
The process of electricity of sodium chloride solution is called
Chlor-alkali process
USES
a) NaOH is used for making the soap and detergent.
b) NaOH is used in purifying bauxite ore and thus obtaining aluminum
metal.
c) NaOH is used for making paper and rayon.
a) Chlorine is used to sterilize drinking water.
b) Chlorine is used to make CaOCl2.
c) Chlorine is used to make CFC, PVC,
a) H2 is used in conversion of oil to ghee.
b) H2 is used in production of HCl, Ammonia, Methanol etc.
c) Liquid hydrogen is used as fuel in rocket.
WASHING SODA
Chemical formula of washing soda is sodium carbonate decahydrate
(Na2CO3.10H2O)
PRODUCTION
NaCl + NH3 + H2O + CO2 NaHCO3 + NH4Cl
NaHCO3 Na2CO3 + CO2 + H2O
Na2CO3 + 10H2O Na2CO3.10H2O
USES
a) Washing soda is used as a cleaning agent like washing clothes.
b) Washing soda is used to remove permanent hardness of water.
c) Washing soda is used in manufacture of glass, soap and paper.
PROPERTIES
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a) Washing soda is a transparent crystalline solid.
b) Washing soda is one of the few metal carbonates that are soluble in
water.
BAKING SODA
Chemical name of baking soda is sodium hydrogen carbonate. It represented
by formula NaHCO3.
PRODUCTION
NaCl + NH3 + H2O + CO2 NaHCO3 + NH4Cl
USES
a) Baking soda is used as an antacid in medicine to remove acidity of
stomach.
b) Baking soda is used to form baking powder.
NaHCO3 + H+ Na+ + CO2 + H2O
Baking powder is a mixture of soda and edible acid as tartaric acid.
c) Baking soda is used in fire extinguishers.
NaHCO3 + H2SO4 Na2SO4 + CO2 + H2O
PROPERTIES
a) Sodium hydrogen carbonate is a mild, non-corrosive base.
b) On heating baking soda form soda ash.
c) It consists of white crystals which is sparingly soluble in water.
BLEACHING POWDER
Bleaching powder is a calcium oxy-chloride and chemical formula is CaOCl2
also called chloride of lime.
PRODUCTION
Ca(OH)2 + Cl2 CaOCl2 + H2O
(Slaked lime) (Bleaching powder)
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USES
a) It is used for disinfecting drinking water supply that make water germ
free.
b) It is used for manufacture of chloroform (CHCl3).
c) It is used for making wool un-shrinkable.
d) It is used for facial and also used in textile industries.
PROPERTIES
a) It is white powder that has strong smell of chlorine.
b) It is soluble in cold water.
c) CaOCl2 + H2SO4 CaSO4 + Cl2 + H2O
The real bleaching agent is Cl2 that change colour of hair black to
brown.
PLASTER OF PARIS
Its chemical formula is calcium sulphate hemi-hydrate and formula is
CaSO4.1/2H2O. It is made in Paris due to that it named as Paris of plaster or
Plaster of Paris. It is commonly named as P.O.P.
PRODUCTION
CaSO4.2H2O 100C CaSO4.1/2H2O + 3/2 H2O
(Gypsum) (P.O.P.)
USES
a) It is used in hospitals for setting of fractured bones in right position.
b) It is used in making of toys, ornaments, statues etc.
c) It is used as fire proofing material.
d) POP is used for designing on the ceilings of houses.
PROPERTIES
a) It is a white powder
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b) It has remarkable property of setting into a hard mass in about half an
hour.
CaSO4.1/2H2O + 3/2H2O CaSO4.2H2O
Due to this POP is stored in a moisture proof container.
CRYSTALLISATION
The water molecules which form part of structure of a crystal are called
water of crystallization.
Salts which contain water of crystallization are called hydrated salt.
Such as: FeSO4.7H2O, CuSO4.5H2O, etc.
When hydrated salt is heated strongly, then they lose their water
molecules thus formed salt called anhydrous salt. Such as:
CaSO4.2H2O CaSO4 + 2H2O
1. What is the milk of magnesia?
2. Name two natural indicators?
3. Is turmeric an indicator?
4. Which gas is evolved when metal carbonates or metal hydrogen
carbonate reacts with dilute acids?
5. Is CO2 gas supporter of combustion?
6. What happens when copper oxide reacts with conc. H2SO4?
7. Which colour is obtained when CuO reacts with conc. HCl?
8. What is the colour of pH paper in NaCl solution?
9. Why does bleaching powder act as bleaching agent?
10. Name the substance which on treatment with chlorine gives bleaching
powder.
11. Why does it act as disinfectant?
12. Why is bread, biscuits fluffy?
13. The acid present in atmosphere of Venus is .......
14. Enamel is made up of......
15. Toothpastes are........in nature.
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16. Write the name and chemical formula of the products formed by
heating gypsum at 373 k. (AI 2010)
17. Write the names and chemical formula of the products formed by the
action of chlorine on slaked lime. (AI 2010)
18. During summer season, a milkman usually adds very small amount of
baking soda to fresh milk. Give one reason. (2009)
19. Name the gas usually liberated when a dilute acid reacts with a metal.
What happens when a burning candle is brought near this gas? (AI
2009C)
20. Which gas is generally liberated when a dilute solution of hydrochloric
acid reacts with an active metal? (Foreign 2009)
21. What is the color of litmus in a solution of ammonium hydroxide?
(Foreign 2009)
22. Two solutions A and B have pH values of 5 and 8 respectively. Which
solution will be basic in nature? (Delhi 2008)
23. On adding dilute hydrochloric acid to copper oxide powder, the
solution formed is blue-green; predict the new compound formed
which imparts a blue-green colour to the solution.(2008)
24. How does the flow of acid rain water into a river make the survival of
aquatic life in the river difficult? (AI 2008)
25. Write chemical equations to show the reactions taking place when a
glass rod dipped in concentrated hydrochloric acid is introduced in a
jar containing ammonia gas. (Foreign 2004)
26. Which acid is present in sour milk or curd?
27. Which acid is present in tamarind?
28. What is aqua regia?
29. Which chemical is present in enamel?
30. Do alkalis also react with metals? Give one example
31. A yellow colour solution turns reddish pink in acidic solution and
remains as such in basic solution. What do you call such substances?
32. Two solutions have pH numbers 7 and 2 respectively. Which solution
has more H concentration?
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33. How is the concentration of hydronium ion (H3O+) affected when a
solution of an acid is diluted?
34. Tooth enamel is one of the hardest substances in our body. How does it
undergo damage due to eating chocolates and sweets? How do tooth
pastes prevent this damage? (CBSE S. paper 2009)
35. A compound which is prepared from gypsum has the property of
hardening when mixed with a proper quantity of water. Identify the
compound. Write the chemical equation for its preparation. For what
purpose is it used in hospitals? (Delhi 2009, AI 2008)
36. What is meant by water of crystallization, of a substance? Describe an
activity to show that blue copper sulphate crystals contain water of
crystallization. (Foreign 2009.Delhi 2008)
37. A compound X of sodium is commonly used in kitchen for making
crispy pakoras. It is also used for curing acidity.
38. What is Baking powder? How does it make the cake soft and spongy?
(Delhi 2008)
39. Write the chemical formula for washing soda. How may it be obtained
from baking soda? Name an industrial use of washing soda other than
washing clothes. (AI 2008)
40. Write the chemical formula for bleaching powder. How is bleaching
powder prepared? For what purpose is it used in paper factories? (AI
2008)
41. Write the chemical formulae of washing soda and baking soda. Which
one of these two is an ingredient of antacids? How does it provide relief
in stomach ache? (Foreign 2008)
42. (a) Give Arrhenius definition of an acid and a base. (b) Choose strong
acid and strong base from the following; CH3COOH, NH4OH, KOH, HCL
(Delhi 2007)
43. A metal compound A, react with dilute hydrochloric acid to produce
effervescence. The gas evolved extinguishes a burning candle. Write a
balanced chemical equation for the reaction if one of the compounds
formed is calcium chloride.
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44. Why does distilled water not conduct electricity whereas rainwater
does?
45. A milkman adds a very small amount of baking soda to fresh milk. (a)
Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
(b) What do you expect to observe when the milk comes to a boil? (c)
Why does this milk take a long time to set as curd?
46. Baking soda is used in small amount in making bread and cake. It helps
to make these soft and spongy. An aqueous solution of baking soda
turns red litmus blue. It is also used in soda acid fire extinguisher. Use
this information to answer the following questions; (i) How does
Baking soda help to make cakes and bread soft and spongy? (ii) How
does it help in extinguishing fire? (iii) Is the pH value of baking soda
solution lower than or higher than? (CBSE 2009)
47. A student dropped few pieces of marble in dilute Hydrochloric acid
contained in a test tube. The evolved gas was passed through lime
water. What change would be observed in lime water? Write balanced
chemical equations for the reaction when (a) gas was evolved (b) gas
was passed through lime water. (CBSE Sample
paper 2009)
48. Answer the following; (a) Why is formula of plaster of Paris written as
CaSO4. ½ H2O? How is it possible to have half a water molecule
attached to CaSO4? (b) Why is Sodium Hydrogen Carbonate an
essential ingredient in most antacids? (c) When electricity is passed
through an aqueous solution of sodium chloride, three products are
obtained. Why the process is called chlor-alkali process? (CBSE
Sample paper 2009)
49. Name the products formed in each case when (a) hydrochloric acid
react with caustic soda. (b) Granulated zinc reacts with caustic soda. (c)
Carbon dioxide is passed into lime water.
50. A compound X of sodium forms a white powder. It is a constituent of
baking powder and is used in some antacid prescriptions. When
heated, X gives out a gas and steam. The gas forms a white precipitate
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with limewater. Write the chemical formula and name of X and the
chemical equation for its decomposition on heating. What is its role in
baking powder and in antacids? (Delhi 2005C) (HOTS)
51. Compounds like alcohols and glucose also contain hydrogen but are not
categorized as acids. Discuss an activity to prove it.
52. What are strong and weak acids? In the following list of acids, separate
strong acids from weak acids. Hydrochloric acid, citric acid, acetic acid,
nitric acid, formic acid, sulphuric acid.
53. Name the acid present in ant sting and give its chemical formula. Also
give the common method to get relief from the discomfort caused by
the ant sting. (HOTS)
54. Salt A commonly used in bakery products on heating gets converted
into another salt B which itself is used for removal of hardness of water
and a gas C is evolved. The gas C when passed through lime water turns
it milky. Identify A, B and C. (HOTS)
55. A metal carbonate X on reacting with an acid gives a gas which when
passed through a solution Y gives the carbonate back. On the other
hand a gas G that is obtained at anode during electrolysis of brine is
passed on dry Y, it gives a compound Z, used for disinfecting drinking
water. Identity X, Y. G and Z. (HOTS)
56. A sulphate salt of Group 2 element of the Periodic Table is a white, soft
substance, which can be moulded into different shapes by making its
dough. When this compound is left in open for some time, it becomes a
solid mass and cannot be used for moulding purposes. Identify the
sulphate salt and why does it show such a behaviour? Give the reaction
involved. (HOTS)