1

CHAPTER –I

RATE OF CHEMICAL REACTION AND CHEMICAL EQUILIGBRIUM 1. Which of the following reactions are slow and which are the fast? i) Setting of cement. ii) Formation of coal in the earth crust. iii) Reaction between aqueous solution BaCl2 and H2SO4. Ans.

(i) Setting of Cement. Fast reaction. (ii) Formation of coal. slow reaction. (iii) Rect. Bet. (Aq) BaCl2 & H2SO4. Fast reaction.

2. Give one example in case of a reaction, which takes place i) Instantaneously. ii) At moderate rate. Ans.

(i) Instantaneously

a. Silver nitrate + sod. Chloride silver Chloride + sod. Nitrate AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq) b. Barium Chloride + Hydrogen Sulphate Barium sulphate + Sodium Chloride. BaCl2(aq) + H2SO4 BaSO4(s) + 2HCl(aq) c. 2Mg + O2 2MgO

ii) Moderate. a.CH3COOH (aq) + C2H5OH(aq) H2SO4 CH3COOC2H5 + H2O

MnO2

b.2KClO3 2KCl + 3O2

3. How will you define the rate of a chemical reaction? What is the meaning of average rate of chemical reaction? Ans. The rate of disappearance of a reactant or reactants (OR)

2 The rate of appearance of a product or products (OR) Rate of reaction = Change in conc. Of a reactants or products Time taken Eg: NO2(g) + CO(g) CO2(g) + NO(g) Rate of reaction = -Δ[NO2] = -Δ[CO] = Δ[CO2] = Δ[NO] Δt Δt Δt Δt 4. What are various factors, which affect the rate of a chemical reaction? Explain with the suitable examples. Ans; The rate of a reaction depends upon the following factors

a) Concentration of the reactants. b) Effect of Temperature. c) Effect of Catalyst. d) Effect of Light/radiation. e) Surface area of the reactants. a) Concentration of the reactants:

The rate of a reaction generally increases with increase in Concentration of reactant of reactants. For example in 2NO+O2-->2NO2 reaction, the reaction rate doubles when O2 concentration doubles. The rate of reaction quadruples when “NO” concentration doubles. (b) Effect of Catalyst: Catalysts are substances, which alters the rate of chemical reactions with out undergoing any significant change. If the catalyst increases the rate of reaction it is named as positive catalysts. Fe N2+3H2 2NH3 Fe is +ve catalyst NO 2SO2+O2 2SO3 NO is +ve catalyst If the catalyst decreases/retards the rate of reaction it is named as negative catalyst. Glycerol Eg: 2H2O2 2H2O + O2 Glycerol is –ve catalyst

3C) Effect of Light/Radiation Rates of some reactions are influenced by light. For example photosynthesis, photography. Blue printing such type of reactions are called photochemical reactions. Light 6CO2 + 6H2O C6H12O6 Light 2 AgBr 2Ag + Br2 Light H2 + Cl2 2HCl d) Effect of Temperature: The rate of the reaction increases with increase of temperature. Perishable foods like milk, cooked vegetables go bad much more rapidly in summer than in winter. In the case of enzyme catalyzed reaction rate of reaction increases with in creases of temperature at first up to a certain optimum temperature and then rate of reaction decreases with increase of temperature.

f) Surface area of the reactants:

The rate of the reaction increases with increase in surface area of the reactants. The smaller the size of reactant particles the greater is the total surface area exposed for reaction and consequently greater is the rate of the reaction. For Eg: Zn + 2HCl ZnCl2 + H2↑ fast (dust) Zn + 2HCl ZnCl2 + H2↑ (Granules) 5. What is the role of a catalyst in a reaction? Does catalyst undergo any

e at the end of a chemical reaction? changAns. A catalyst is a substance, which alters the rate of a chemical reaction. A catalyst may increase or decrease the rate of a reaction. Fe/Mo Eg: N2 + 3H2 2NH3 (Catalyst) Fe/Mo increases the rate of reaction. So Fe/Mo is called +ve catalyst.

4 Glycerol 2H2O2 2H2 O + O2 (Catalyst) Glycerol decreases the rate of reaction. So glycerol is –ve catalyst.

No, Catalyst doesn’t undergo any change chemically. A Catalyst may be recovered in mass and composition at the end of the chemical reaction.

6. What is the effect of temperature on the following? i) Dissociation of an electrolyte (dissolution is taken as an endothermic process). ii) Rate of a reaction in gaseous state. iii) Concentration of product(s) of an exothermic reversible reaction carried out in a closed container. Ans. i)Increases. ii) Increases. Iii) Decreases. 7. What do you mean by dynamic equilibrium? In what way is it different from static equilibrium? Explain with suitable examples. Ans. In a reaction at the equilibrium the rate of forward reaction is equal to the rate of backward reaction. In other words forward and back word reaction continues even after equilibrium is reached. So equilibrium is dynamic. N2(g) + 3H2(g) 2NH3(g) 8. Can we achieve equilibrium between water and its vapour in an open container? Explain your answer and say what will happen eventually? Ans. No; we can’t achieve equilibrium between water and its vapour in an open container. Water vapour escapes into atmosphere. 9. Which of the following processes will be at equilibrium? i) Water maintained at 233K in a closed container. ii) Sulpher dioxide being released in atmosphere at 298K. iii) Heating of calcium carbonate at 773K in a closed kiln. Ans. i) H2O(l) H2O(g) At Equilibrium

5 (Liquid water ) (Water vapour) ii) 2SO2 + O2 2 SO2 iii) CaCO3 CaO + CO2 At Equilibrium 10.Which of the following reactions will favour the formation of product(s) when the temperature is raised by 100C and reaction is carried out in a closed container i) N2(g) + 3H2(g) 2NH3(g)+ 92KJ ii) 2Cl2(g) + 2H2O(g) 4HCl(g) + O2(g) -113KJ Ans (i) N2(g) + 3H2(g) 2NH3(g) + 92KJ The reaction is carried in closed container means reactant and products are in dynamic equilibrium. On increasing the temperature the equilibrium shifts towards (exothermic side) left and ammonia will decompose to give N2 and H2. (OR) Equilibrium shifts back (Left side) ii) 2Cl (g) + 2H O(g) 4HCl(g) + O (g) -113KJ 2 2 2

As the reaction is carried out in closed container, it is in equilibrium. On increasing the temperature the equilibrium shifts towards right. 11. Write the equilibrium constant for the following reactions i) 2NO2(9) N2O4(g) ii) 2SO2(g) + O2(g) 2SO3(g) iii) CO(g)+ 3H2(g) CH4(g) +H2O(g) iv) Fe3+ (aq) + SCN(aq) FeSCN2+(aq) Ans.

6 (i) 2NO2(g) N2O4(g) KC = [N2O4] [NO2]2 ERROR (ii) 2SO2(g) + O2(g) 2SO3(g) KC = [SO3]2 [SO2]2[o2] (iii) CO(g)+ 3H2(g) CH4(g) +H2O(g) KC = [CH4]+[H2O] [CO][H2]3

(iv) Fe3+ (aq) + SCN-(aq) FeSCN2+(aq) K = C [FeSCN2+] [Fe3+ -][SCN ] 12. Classify the following acids and cases in the categories of weak and strong i) HCl ii) H SO iii) CH COOH iv) HCN v) HClO vi) H PO vii) NaOH viii) Ca(OH) ix) NH OH

2 4

3

4

3 4

2

4

Ans. Strong acids: HCl, H2SO4 ,HClO4 . Weak acids: CH3COOH, HCN,H3PO4 Strong bases: NaOH Weak bases: NH4OH, Ca(OH)2 13.Find the PH of the solutions if the acids are fully dissociated. i)0.01M Hcl ii)o.o5M H2SO4Ans: i) 0.01M Hcl.

HCl H+ + Cl- 0.01M 0.01M [H+] = 0.01M = 1/100 M = 10-2M PP

H = - log [H+] = -log [10-2]

7 = -(-2log 10) = -(-2) = 2.00

ii) 0.05M H2SO4 H2SO4 2H+ + SO42-

(0.05M) (0.10M) [H+] = 0.10M = 1/10 M = 10-1M

PP

H = -log [H+] = -log [10-1] = -1(-1 log10) = -1(-1) = 1.00

14. Classify the following into strong and weak electrolytes on the basis of their behaviour in aqueous solution. I) NaCl ii) NH4 Cl iii) CH3COOH iV) HCN V) NaOH Ans. Strong electrolytes Weak electrolytes NaCl CH3COOH NH4Cl HCN NaOH 15. Calculate the PH of the solution when hydrogen ion concentration is i) 1.0x10-7M ii) 1.0x10-9M Ans. PP

H = -log [H+] =-log [1.0x10-7]

=-log [log10-7] =7log10

=7[1.0000] =7.00

8 PP

H = -log [H+] = -log [1.0x10-9] = -log [10-9] = 9[1.0000] = 9.00 16. At 298M equilibrium concentrations of the reactions and products for the reaction H (g) + I (g) 2HI(g) are as follows: [HI] = 0.490M. [H ] =0.080M and [I ] = 0.060M Calculate the equilibrium constant at this temperature

2 2

2 2

Ans. H2(g) + I2(g) 2HI(g) [H2]=0.080M; [I2]=0.060M; [HI]=0.490M. [HI]2 [0.49M]2 KC = = [H2] [I2] [0.080M][0.060M] 0.2401 = =50 0.0048 17. Equlibrium constants for the reactions given below are provided in the right hand side at 298K. (i) N2O4(g) 2NO2(g) KC=4.66x10-3 (ii) 2NH3 N2(g) +3H2(g) KC= 3.0x10-9 Ans. In which case, formation of the products will be more favoured? KC is directly proportional to the conc. of products. So the reaction in which Kc value is more will be favorable for the formation of more products. (i) N2O4(g) 2NO2(g) KC=4.66x10-3 (ii) 2NH3 N2(g) +3H2(g) KC= 3.0x10-9 KC of first reaction (4.66x10-3) is more than the KC of second reaction. Hence, the Product formation will be more favoured in the case of first reaction N2O4(g) 2NO2(g)

9

CHAPTER-2

SOME IMPORTANT CHEMICAL COMPOUNDS

1. Give the Names of Raw Materials that are required for the manufacture of

washing soda by solvay process. Write the reactions involved in the process.

Ans:

Common salt : NaCl.Sodium chloride. Ammonia : NH3 .Ammonia Lime Stone : CaCO3.Lime stone (Calcium carbonate) H2O + NH3 + NaCl + CO2 NaHCO3 + NH4Cl

Heat 2NaHCO3 Na2CO3+ CO2+H2O Heat

CaCO3 CO2+CaO CaO + H2O Ca (OH)2

Ca(OH)2+ 2NH4Cl CaCl2 +2NH3+2H2O 2. What is efflorescence? Name one compound which shows efflorescence? support your answer with reaction? Ans:

The processes of loosing water of crystallization, when the

substance is exposed to air for long time to form anhydrous or monohydric

substance is called as efflorescence.

Na2CO3 10 H2O, Sodium carbonate deca hydrate is one example.

10

Na2CO3 10 H2O Na2CO3 H2O + 9H2O

3. State the important properties of washing soda. Ans: PHYSICAL PROPERTIES: Washing soda is a transparent crystalline solid. Washing soda is soluble in water. Washing soda solution in water is alkaline which turns red litmus blue. Washing soda is good cleansing agent which even works well with hard water. Washing soda shows Efflorescence. CHEMICAL PROPERTIES: 1) Action of heat: Heat Na2CO3 1OH2O Na2 CO3 + 10H2O 2) Action with dil. HCl Na2CO3 + 2HCl 2NaCl + CO2 + H2O 3) Action with CO2 Na2CO3+SiO2 Na2SiO3+CO2 Sod. Silicate (soft glass) 4.What is the common name of Na2Co3. 10H2O? Name a metal carbonate which is soluble in water. Ans: Common name of Na2CO3.10H2O is Washing soda. Metal carbonate Soluble in water is sodium carbonate or soda ash Na2CO3 5. Give important uses of washing Soda? Ans: Washing soda is used as cleaning agent in laundry and for domestic purpose. Washing soda is used for softening hard water Washing soda is used in the manufacture of borax, glass,soap etc. Washing soda is used as laboratory reagent in qualitative and quantitative

11analysis. 6. Give important properties of baking soda Ans: PHSICAL PROPERTIES: 1. Baking soda is white in color. 2. Baking Soda is sparingly soluble in water. 3. Baking soda solution with water is alkaline and turns red litmus to blue. CHEMICAL PROPERTIES Action of heat: Baking soda gives CO on heating Heat 2NaHCO Na CO + H O +CO Action of dil. Hcl HCl + NaHCO NaCl + CO + H O 7. A baker found that the cake prepared by him is hard and small in size. Which ingredient has he forgotten to add that would have made the cake Fluffy? Give reason.

2

3 2 3 2 2

3 2 2

Ans: Baker forgotten to add NaHCO3, Baking soda. NaHCO3 in the form of baking powder is added to dough for preparing cake or bread. NaHCO3 on heating with food material decomposes to form CO2 due to which cake or bread becomes light, fluffy and big in size. 2NaHCO3 Na2CO3 + CO2 + H2O 8. Name the substance obtained by the action of chlorine on dry slaked lime write chemical equation of the reaction. Ans: Calcium oxychloride (Bleaching Powder) is obtained by the action of Chlorine gas,Cl2 on dry slaked lime Ca(OH)2. Ca(OH)2 + Cl2 CaOCl2 + H2O (Slaked lime) (Bleaching powder) 9. How is bleaching powder prepared? Give the reaction? Ans: Bleaching Powder is prepared by passing chlorine gas over dry slaked lime. Ca(OH)2 + Cl2 CaOCl2 + H2O

12 10. What happens when beaching powder is exposed to air? Ans: Bleaching powder deteriorates giving off chlorine gas (Cl2) due to the reaction with carbondioxide gas present in air CO2 CaOCl2 + CO2 CaCO3 + Cl2 11. What are the important uses of bleaching powder? Ans: It is used for disinfecting drinking of water. It is used for bleaching cotton in textile industry. It is used for bleaching wood pulp in paper industry. It is used for the manufacture of chloroform,CHCl3 It is used as an oxidizing agent in chemical industries and laboratory. 12. Name the compound which is used in hospitals for setting fractured Bones. Write its chemical name and formula. How is it prepared? Ans: Plaster of Paris (Calciumsulphate hemi hydrate) CaSO4 ½ H2O is used in hospitals for setting fractured bones. Calcium sulphate hemi hydrate,CaSO4 ½ H2O It is prepared by heating Gypsum at 373k (1000 C)

1000C CaSO4 2H2O CaSO4 ½ H2O + 3/2 H2O 13. What is gypsum? What happens when gypsum is heated to 373K? Ans: Calcium sulphate dehydrate is called as Gypsum. CaSO4 2H2O is Gypsum 1000c CaSO4 2H2O CaSO4 ½ H2O + 3/2 H2O 373 k Gypsum on heating at 373k forms plaster of Paris, CaSO4 ½ H2O 14. Give chemical equation for the preparation of lime?

ANS: Heat

CaCO3 CaO (s) + CO2 (g)

13(Lime)

Calcium carbonate (Lime Stone) on heating in a lime kiln forms lime. 15. Give important uses of plaster of Paris? Ans: It is used in making toys, decorative material, jewellery, cosmetics and casts for statues. It is used for setting fractured bones in the right position. It is used for sealing the air gaps in apparatus to make it air tight. It is used for making smooth surfaces and ornamental designs. 16. How is slaked lime obtained from lime? Ans: Lime (Cao) reacts with water to form slaked lime Ca(OH)2 CaO + H2O Ca(OH)2+ Heat 17. What happens when lime stone is heated strongly? Write the chemical equation. Ans: Lime stone is calcium carbonate CaCo3, it decomposes to form quick lime Cao and CO2 on heating. CaCO3 CaO + CO2 (Lime Stone) (quick lime) 18. A white powdered solid, when added to water produces a hissing sound. Identify the compound. How this compound does reacts with moist hydrogen chloride gas? Write the chemical equation. Give two uses of the same compound. Ans: White powdered salt that produces hissing sound is lime CaO.(Calcium oxide) CaO + H2O Ca(OH)2+Heat It reacts with moist HCl to form CaCl2 and water. CaO + 2HCl CaCl2+H2O Uses of CaO i) CaO is used in manufacture of glass, cement, etc., ii) Cao is used as basic lining in furnaces. iii) Cao is used for white washing. iv) CaO is used in manufacture of bleaching powder.

1419. How is Cement manufactured? Ans: The raw materials used for the manufacture of cement are i) Lime Stone (to provide CaO) ii) Clay(to provide Al2O3, SiO2, Fe2O3) The raw materials lime stone and clay are finely powdered and then mixed togather in the ratio 3:1 by mass. This mixture is made into homogenous by wet or dry processes. The finely Homogenized mixture of clay and lime stone is heated in a rotary kiln to produce CLINKER. The clinker is made in to fine powder and 2to5% gypsum is added to regulate the setting time. Diag: Ref.page number 20 fig.number2.4 20. Give some important uses of cement. Ans: For making 1. Mortar:- Cement is mixed with sand and required amount of water. This mixture is called as mortar, which is used for plastering and binding bricks and stones. 2. For making Concrete:- It is a mixture of cement, gravel sand and water, which is used in construction of buildings, dams, roads etc., 3. For making Reinforced concrete cement: Steel rods or steel frames are embedded in concrete, which useful in construction of dams, buildings, and bridges. 21. What are the raw materials used for making glass? Ans: Sodium carbonate (soda ash) Na2CO3 Lime Stone (Calcium Carbonate) CaCO3 Sand (Silica, Silicon dioxide) SiO2 Broken Glass pieces (Cullet) 22. Describe the process of manufacture of ordinary glass? Ans: Raw Materials: soda ash (Sodium Carbonate, Na2Co3) Lime Stone (Calcium Carbonate, CaCo3) Silica (Silicon dioxide SiO2) Cullet (Broken Glass) The powdered raw materials soda ash, lime stone, silica is known as batch, broken glasses are add to the raw materials and then heated to 14000C (1673K) in the furnace. Cullet lowers the melting point of the batch. The following chemical reactions takes place to form molten glass, over molten glass scum is formed. The scum is skimmed off.

15 Na2CO3+SiO2 Na2SiO3 + CO2 CaCO3 + SiO2 CaSiO3 + CO2 The molten mixture of Na2SiO3 and CaSiO3 forms Solid glass on Cooling. Na2SiO3+CaSiO3 + n SiO2 Na2SiO3. CaSiO3 nSiO2 (Glass) 23. How does Pyrex glass differ from soda glass? Ans:

Soda Glass 01.It doesn’t contain boron and

Aluminum oxides. 02. It is prepared by fusing Na2CO3,

CaCo3 03. It is called Soft Glass because

it softens easily on heating. 04.It is easily attacked by chemicals 05.It has high coefficient Of

expansion so it is unfit for making laboratory apparatus

06.It is brittle and breaks easily

Pyrex Glass 01.It Contains boron and aluminum

oxides also o2.It is prepared by fusing

Na2CO3,K2CO3,CaCO3,SiO2, AlO3and borax.

03.It is very difficult to soften Pyrex glass by heating

04.It is more resistant to chemicals 05.It has low coefficient of

expansion so it is used for making laboratory apparatus

06.It is hard

24. What do you mean by annealing of glass? Ans: The process of cooling finished glass article very slowly and uniformly is called annealing. The annealing is so slow it will take sever days for completion. Annealing prevents brittleness in glass 25. What are the applications of photo chromatic glasses? Ans:

1. Photo chromatic glasses are used as sunshield glasses. 2. Photo chromatic glasses are used for making spectacles, goggles and cameras.

1626. What are the different kinds of glasses? Mention their uses. Ans:

Soda Glass(or soft glass) Uses: for making * Glasses tumblers. * Dishes. * Bottles. * Mirrors. * Window panes. * Bulbs etc. Hard Glass (or Potash Glass) Uses: For making * hard glass laboratory apparatus. * Glass bottles in which acids and bases are to be preserved. Lead Crystal Glass Uses: For making * Expensive Glassware. * Decoration pieces. * Cut glass articles. 27. How is steel manufactured by Bessemer process? Ans: For fig ref.page number 22 fig.number2.6.

Steel is manufactured from pig iron in a Bessemer converter, which is a pear shaped furnace lined inside with silicon. Molten pig iron is taken in Bessemer converter is heated with a hot blast of air. Oxygen present in the hot air reacts with impurities like Mn, Si, C, P to form oxides some of these oxides escape into atmosphere and rest forms slag. This slag is skimmed off. When all the impurities are removed, required amount of carbon is added to molten iron to form steel of our choice. The following reactions take place in Bessemer converter. 2Mn + O2 2MnO Si + O2 SiO2 2C + O2 2CO 4P + 5O2 2P2O5 3CaO+ P2O5 Ca3(PO4)2 slag MnO +SiO2 MnSiO3 slag CaO +SiO2 CaSiO3 slag 28.Give important properties of Steel? Ans:

Properties of steel depends on percentage of steel Iron containing 0.1

17to 0.4 percent of carbon is mild steel * Quite malleable. * Ductile * Elastic * Very tough * Not brittle Iron containing 0.5 to 1.5 percent of carbon is hard steel * Very hard * Brittle * High elasticity

29. What are the important uses of steel? Ans:

01. Steel with 7 to 20% Manganese is very hard and tough used for Helmets, Rock crushing machinery. 02. Chromium and nickel steel is used for making a aeroplane parts, motor cars, bicycle, parts, radio valves, bulbs. 03. Cobalt steel is used for making permanent magnets. 04. Silica steel is used for making pipes and pumps which carry acids. 05.Tungsten chromium vanadium steel used or making drilling tools. 06.Stainless steel is used for making utensils surgical instruments etc.

18

CHAPTER 13

Metal and Non Metals 1. What are metals?

Metals are the elements (except Hydrogen) which form positive ions by losing electrons. (Or) Metals are the elements (except hydrogen) which form positive ions by losing electrons and posses good electrical conductivity metals and ductile Example: Na Na+ + 1e-

Mg Mg2+ + 2e-

2. Explain why the surface of some metals acquires, a dull appearance

when exposed to air for a long time?

Metals react with oxygen, hydrogen sulphide, and carbon dioxide to form metal oxide, metal sulphide and metal carbonates. So metals acquire dull appearance which exposed to air for longtime. For eg: (O2) CO2Na Na2O Na2CO3 (air) H2S 2Ag Ag2S (air)

193. What are amphoteric oxides? Give examples of two amphoteric oxides.

Metal oxides which show both acidic, as well as basic in nature are amphoteric. Eg:Al2O3 Aluminum Oxide Zno Zinc Oxide

4. Name two metals which do not react with oxygen.

Ag – silver. Au – gold. Pt – Platinum.

5. Which gas is produced when a metal reacts with dilute hydrochloric acid? Write the chemical reaction when iron reacts with dil. H2SO4

Hydrogen gas is produced. Fe(s) + H2SO4(aq) FeSO4(aq) + H2(g)

6. Name two metals which can form hydrides with hydrogen.

Na – Sodium Ca – Calcium 2Na(s) + H2(g) 2NaH(s) (sodium hydride) Ca(s) + H2(g) CaH2(s) (Calcium hydride)

7. What would you observe when zinc is added to a solution of iron(II) sulphate? Write the chemical reaction that takes place. Observations (i)Pale green colour of the solution slowly changes to colourless. ii)Iron is formed slowly at the bottom of the reaction vessel. Zn(s) + FeSO4(aq) ZnSO4(aq) + Fe(s) (Pale green) (Colorless)

8. Describe briefly the froth flotation process for the concentration of sulphide ores.

Fig: Ref. Page NO 170 of X std science and technology textbook fig No: 14.2. This forth floatation process is used to separate the gangue from sulphide ores in which ore particles are lighter and gangue particles are heavier. Powdered ore particles, pine oil and water mixture is mechanically agitated by blowing air with high pressure as shown in the above figure. Forth formed in this process rises up with lighter sulphide ore particles. This forth is skimmed off which gives are particles and heavier gang particles shinks to bottom of the tank.

209. Define the term metallurgy.

The extraction of metals from their ores and then refining the metal for their use is known as metallurgy.

10. Does every mineral have a definite and fixed composition? Explain. No, Every mineral doesn’t have a definite and fixed composition. Some minerals may contain a large percentage of metal where as others may contain only a small percentage of metal. Some minerals may contain objectionable imparities which may hamper the extractions of metals. The mineral which has high percentage of metal and very less objectionable impurities is known as ore from which metals are extracted Profitably. 11. What is bauxite? What are the main impurities that are found in this

ore? Briefly describe how the ore is purified. Al O , Bauxite is the ore of Aluminum. Impurities are sand and iron 2 3 Oxide. Purification: Bauxite is purified by Bayer’s process.In this Process powdered ore is treated with aq. NaOH solution. Iron (III) oxide and sand do not dissolve in sodium hydroxide solution. So they are separated by filtration. Al O reacts with NaOH to form sodium 2 3 aq aluminate. Sodium aluminate converted into aluminum hydroxide Al(OH)3 Which on heating produces Alumina Al2O3? NaOH(aq) H O X 2 Al O NaAlO Al (OH) Al O2 3 2 3 2 3 Impure sod.aluminate pure 12. Differentiate between roasting and calcination. i) In calcination the ore is heated in the absence of air where as In roasting ore is heated in the presence of air. ii) calcination is done for carbonate ores where as Roasting is done for sulphide ores 13. What is a Thermit reaction? Highly reactive metals like aluminum Al can be used as reducing agent to reduce manganese dioxide MnO , and Iron(III) oxide into Mn and Fe. 2 This reaction is called as thermite reaction. 3MnO2(s) +4Al(s) 3Mn(s) + 2Al2O3(s) Fe2O3(s) +2Al 2Fe(s) + Al2O3(s) [OR] Al MnO2 Mn Heat

21 Al Fe O Fe 2 3 Heat 14. Name the various processes used for refining of metals. Which

method is used for refining volatile metals?

i. Liquation Method ii. Distillation Method iii. Electrolytic refining

Distillation method is used for refining volatile metals like mercury and zinc. 15. Name two metals which will displace hydrogen from dilute acids, and

two metals which will not displace.

Metals which displace hydrogen from dilute acids are Na-Sodium Mg-Magnesium Zn-Zinc Fe-Iron Metals which do not displace Hydrogen are

Cu –Copper Au –Gold Ag –Silver

16. In the electrolytic refining of a metal M, name the anode, cathode and the electrolyte.

M is aluminum Anode : Graphite rods Cathode : Graphite lining Electrolyte : Na3AlF6 Cryolyte.

17. What are the different functions of cryolite in the extraction of aluminum by electrolytic reduction of alumina?

1. To lower the melting point of Alumina 2. To act as electrolyte

18. What type of solution-acidic, basic or neutral, is formed by

dissolving the oxides of Group 1 in water?

Basic (alkaline)

19. What important properties of aluminum are responsible for its great demand in industry?

1. High electrical conductivity, 2. High malleability 3. High ductility 4. High resistance to corrosion 5. Light in weight

2220. Draw the cell for the electrolytic reduction of alumina? Why must

the anodes be replaced from time to time?

Ref Page No; 174; fig 14.5 Oxygen gas is liberated at anode, which reacts with graphite (carbon) of anode to form CO2 gas, due to which graphite anode is to be replaced. C + O CO2 2(Carbon at anode) (Oxygen lib.at anode) carbon dioxide

21. Name the raw materials required for extracting iron.

1. hematite Fe O or magnetite Fe3O4 2 32. Lime stone CaCO3 3. Coke

22. Write the chemical reactions that take place in the blast furnace

for the extraction of iron from hematite. C(s) + O2(g) CO2(g) + Heat

CaCO3(s) CaO(s) + CO2(g)

CaO + SiO2 CaSiO3(slag)

Fe2O3(s) +3CO(g) 2Fe(a) + 3Co2(g)

23. Why is iron more useful when it is mixed with a little carbon? When small amount of carbon 0.1 to 1.5 percent added to pure Iron it forms an alloy called steel it is 1) Hard 2) strong 3)Less Rusting. 24. What is the difference between pig iron and steel? Pig Iron(cast Iron):- Pig Iron contains about 4 percent carbon as impurity along with other impurities like sulphur, phospurous, silicon and manganese. Pig iron is very hard and brittle which is unfit for many uses. Where as Steel: Steel is an alloy Iron and 0.1 to 1.5% of carbon. Which can

be used for making nails, screws, girders, bridges, railway lines etc.,

25. Why is limestone added to the blast furnace? CaCO CaO + CO3

2

Lime stone on heating produces calcium oxide, CaO which acts as flux to removes silicon dioxide, SiO2 from ore as slag. 26. What is 24 carat gold? How will you convert it into 18 carat gold?

24 carat gold means pure gold.

2318 carat gold can be prepared by mixing 18 parts of god and 6 parts of copper/silver.

27. Name an alloy of a. Aluminum used in the construction of aircrafts b. Lead used in joining metals for electrical work and c. Copper used in house hold vessels.

i) Duralumin (Al,Cu,Mg,Mn) ii) Solder (Pb,Sn) iii) Brass ( Cu, Zn) 28. Name the reducing agent which reduces the iron ore in the blast

furnace. Carbon (or) carbon monoxide 29. Name the iron compound in hematite. Write its chemical formula. Hematite, Fe2O3 30. A light and strong alloy is required for making the bodies of

aircrafts. Name this alloy. What are its constituents? Duralumin Constituents:Aluminum Al,Copper Cu,Magnesium Mg, Manganese Mn 31. State two ways to prevent rusting of iron. i) Rusting of Iron can be prevented by painting. ii) Rusting of Iron can be prevented by applying grease or oil. iii) Rusting of Iron can be prevented by Cr/Tin/Zinc plating. iv) Rusting of Iron can be prevented by making it as steel. 32. Differentiate between metals and non-metals. Metals Non-Metals 1. Metals are malleable and 1. Non-metals are neither ductile malleable nor ductile 2. Metals are good conductors 2. Non-metals are bad conductors of heat and electricity of heat and electricity Except “c’in the form of graphite 3. Metals are lustrous 3. Non-metals are not lustrous 4. Metals forms basic oxide 4. Non-metals form acidic or neutral oxides 5. Metals react with “Hydrogen” 5. Non-metals react with “hydrogen” to form metal hydrides, to form non-metal hydrides which are ionic which are co-valent 6. Metals form Metals chlorides 6. Non-metals from non-metal which are ionic chlorides when are covalent 7. Metals are Electro positive 7. Non-metals are not Electropositive 33. What type of oxides is formed when non-metals combine with oxygen? Non-metals react with oxygen to form acidic oxides or neutral oxide Eg: C + O2 CO2(Acidic)

24 C + ½O2 CO(Neutral) S + O2 SO2(Acidic) 4P + 5O2 2P2O5(Acidic) 34. Write the chemical reactions that take place during the manufacture

of hydrogen from natural gas. CH4(g) + H2O(l) CO(g) + 3H2(g) CO(g) + H2O(l) CO2(g) + H2(g) CO2(g) + H2O(s) H2CO3(aq)

35. Give reasons

i) Metals replace hydrogen from dilute acids, whereas non-metals do not ii) Carbonate and sulphide ores are usually converted into oxides.

Metals are more electropositive. It means that some metals lose electrons more readily than hydrogen. So they are able to replace hydrogen from dilute acids. where as

Zn + 2HCl ZnCl2+H2 Mg + H2SO4 MgSO4+H2

Non metals are less electropositive (more electronegative) it means that non-metals gains electrons more readily than hydrogen.

ii)Carbonate and sulphide ores are usually converted into oxides. It is easier to obtain metal from their oxides than from carbonates or sulphides by using simple coke (carbon). So carbonates and sulphides are converted into metal oxides by calcinations and roasting. 36. Name all the products formed when ammonia is passed over heated Copper (II) oxide. 3CuO + 2NH 3Cu + N + 3H O 3 2 2

Copper (II) oxide Ammonia copper nitrogen water Products: Cu Copper N2 Nitrogen H2O Water

37. Ammonia is manufactured from nitrogen and hydrogen by Haber process. The process is carried out at 200-300 atm and 723-773k (i) Give one reason for not using a lower temperature. (ii) Give one reason for not using a very high pressure. (iii) How could ammonia be separated from the other two gases?

25 i) At low temperature, the reaction becomes very slow due to which the rate of formation of ammonia becomes very slow. A moderate temperature of around 4500C to 5000C is used in practice for better yield of NH3 4500c N2 + 3H2 2NH3

ii) Though the formation of Ammonia is favored by high pressure, it is very expensive to construct reaction vessel which can withstand very high pressure, so a moderate pressure of about 200 to 300 Atm is used in Practice. 300Atm N2 + 3H2 2NH3 45O0C iii) The reaction mixture consisting of N2,H2 & NH3 is cooled to below 00C (below 273k) NH3 gets liquefied and recovered. 38. Describe briefly the Frasch process for the extraction of sulphur. Fig 14.12 page No: 183 A set of three concentric pipes are bored into sulphur bed.

Superheated is pumped in to bed through outer pipe along with compressed air through inner pipe. Mixture of molten suphur and water comes out of the bed through middle pipe. Sulphur is insoluble in water and can be separated easily.

39. Define allotropy. Name an allotrope of sulphur which is stable at

room temperature. Existence of of an element in two or more physical forms is called as

allotropy. i) Rhombic sulphur ii) Monoclinic sulpher. Rhombic sulphur is more stable at room temperature.

40. Describe briefly the action of heat one sulphur. (i) At 388K, it melts to form a clear mobile yellow coloured liquid which flows like water. (ii) At about 453K, it becomes thick and orange red and cannot be poured out even if the vessel is inverted. (iii) Upto 523K, it remains viscous, but the colour becomes almost black (iv) Above 523K the viscousity decreased and at 673 K, it is again a dark mobile liquid. (v) Above 713 K, the liquid begins to boil and gives yellow brown

26 Vapours. 41. What would you observe when sulphur dioxide is passed through (i) lime water; (ii) acidified potassium dichromate solution? Write the chemical reactions that take place. (i) SO2(g) + Ca(OH)2(aq) CaSO3(s) + H2O(l) SO2 turns lime water cloudy due to formation of calcium sulphite.

On passing excess SO2 cloudyness disappears due to formation of calcium hydrogen sulphite which is soluble in water

CaSO3(s) + H2O(l) + SO2(g) Ca(HSO3)2 ii) 3SO2(g) + 2H+(aq) + Cr2O72-(aq) 3SO42-(aq) + H2O(l) +

2Cr3+(aq) Orange green So2 reduces orange color potassium dichromate solution to green color

chromium sulphate solution 42. In the Contact process for the manufacture of sulphuric. Acid: (i) Name the catalyst. (ii) Name the substance in which sulphur trioxide is dissolved.

(iii) Name the substance which is diluted with water. i) V2O5 Vanadium Pent oxide at 723K ii) Concentrated H2SO4 (iii) Oleum H2S2O7

43. What happens when a crystal of copper (II) sulphate is placed in conc. H2SO4? Explain your observation.

CuSO4 5H2O(s) CuSO4(s)H2O + 5H2O (Blue) (Color less) Copper (II) sulphate slowly turn white, due to remove of water

molecules from copper (II) sulphate crystal. It means that concentrated H2SO4 acts as good dehydrating agent.

44. Write balanced chemical equation for the three chemical reactions that

take place during the conversion o sulphur dioxide to sulphuric acid in the Contact process.

V2O5 2 SO2 + O2 2SO3 SO3 + H2SO4 H2S2O7 H2S2O7 + H2O H2SO4 45. Water should never be added to conc. H2SO4. Why? If water is added to conc. H2SO4 large amount of heat is released at

once, which will convert some water into steam explosively and some

27times it may splash the acid. Hence adding water to conc. H2SO4 is dangerous.

Dilution of conc. H2SO4 is done by adding acid to water slowly and carefully the heat released in this process is slowly absorbed by large amount of water.

46. Why is sulphuric and known as the “King of Chemicals”?

i) The use and production of H2SO4 by a country in a financial Year can be taken as Index for the development of that country in that year.

ii) There is no Industry which doesn’t use H2SO4 directly or indirectly

iii) The uses of sulphuric acid are so wide and important. Hence sulphuric acid is known as “King of Chemicals”

CHAPTER-15 CARBON COMPOUNDS

1.Define the term, functional group and give two examples for it.

Ans:

An atom or a group of atoms on which properties of the carbon compound depends is known as functional group. Eg: - OH Alcoholic - CHO Aldehydic - CO Ketonic - COOH Carboxylic 2. Name the functional groups present in the following compounds. CH3CH2CH2-OH CH3CH2CH2COOH CH3-CH2-CHO

28 CH3COCH2CH2CH3 Ans:

CH3CH2CH2-OH Alcoholic CH3CH2CH2COOH Carboxylic CH3-CH2-CHO Aldehydic CH3COCH2CH2CH3 Ketonic 3. Describe the preparation of ethanol by the fermentation process. Ans:

Fermentation of sugar is a process in which the sugar molecules are broken down in the ethylalcohol and carbon dioxide by the action of enzymes called invertage and zymase which are present in yeast. Molasses the bi-product of the sugar industry is mixed with suitable quantity of water and yeast powder. This mixer is kept in a huge steel tank at 250C to 300C for about 10 to 12 days, during this time fermentation takes place to form C2H5OH and CO2 gas. C2H5OH is recovered from this mixture by distillation. Invertase C12 H22 O11 + H2O C6H12O6 + C6H12O6 (From yeast) Glucose fructose Zymase C6 H22 O16 2C2H5OH + 2CO2 Glucose & Fructose (from yeast) Ethanol 4. What are enzymes? Name the enzymes required for fermentation of sugar cane to ethanol? Ans:

Enzymes are the chemical substances which acts as biological catalysts

in bio-chemical reactions. Eg: 1.Invertage , Zymase, Amylase and Lactase. Enzymes required for fermentation of sugar cane to alcohol are Investase, converts sugar into glucose and fructose. Invertase C12 H22 O11 C6H12O6 + C6H12O6 Sugar (from yeast) Glucose fructose Zymase, converts, Glucose and Fructose into C2H5OH and CO2

295. Which gas is evolved during the process of fermentation ? Ans: CO2; Carbon dioxide.

6. Which of the following reactions represent hydration of ethene? i) CH2 = CH2 + Br2(aq) BrCH2 – CH2Br i) O3 ii) CH2 = CH2 2HCHO+H2O Ii H2/pd H2SO4 iii) CH2 = CH2 + H2O CH3 – CH2OH H2SO4 Ans CH2 = CH2 + H2O CH3 – CH2OH Represents addition of water to ethene(or) hydration of ethene. 07.What is meant by denaturated alcohol ? How is it prepared? Ans:

Ethyl alcohol (ethanol) made into unfit for drinking is called denaturated alcohol.

It is prepared by adding poisonous substances like menthol, pyridine, copper sulphate etc., to ethanol.

08.Give the names of the following : i) an aldebyde derived from ethane ii) A ketone derived from butane iii) The compound obtained by oxidation of ethanol by chromic anhydride (CrO3); and iv) The substance formed on catalytic hydrogenation of methanal Ans:I) Ethanal (Or)Acetaldehyde CH3CHO ii) 2-Butanone (Or) Butanone-2 CH3COCH2CH3 iii) Ethanal (Or)Acetaldehyde CH3CHO iv) Methane CH4 09.Describe Tollen’s test. Write the equations of the reactions involved iAns:

n this test. Tollen’s reagent is ammonical silver nitrate solution containg excess

Ammonium hydroxide. It is prepared by adding NH4OH to aq AgNO3 solution. AgNO3 + 2NH4OH [Ag(NH3)2]NO3 + H2O (Tollen’s reagent) Tollen’s reagent is mild (weak) oxidizing agent, it oxidizes aldehydes

30into carboxylic acids. HCHO + 2[Ag(NH3)2]NO3+ 2NH4OH HCOOH + 2Ag↓ + 2NH4NO3+4NH3+H2O Due to the formation of silver (Ag) in the above reaction test tube/ test vessel shines like silver. So this test is also called as silver mirror test. 11.Give any two uses of methanal ? Ans: 1. Methanol is used with phenol in the manufacture of bakelite and other thermosetting plastic. 2. Methanol is used with Ammonia in Preparation of UROTROPINE which is one of the important medicine for urinary infection. 3. Methanol is used for making formation which is used to preserve Anatomical specimens. 4. Methanol is used for the manufacture of leather and water proofing fabrics. 5. Methanol is used in the manufacture of dyes. 10. Which class of compounds gives positive Fehling’s test? Write the reactions involved in this test? Ans: Aldenydes (-CHO) gives positive Fehlings test. Aldenydes reacts with Fehlings reagent on heating to form red colored Cu2O copper(I)oxide and sodium Carboxylate. HCHO + 2 Cu(OH)2 + NaOH HCOONa + Cu2O + 3H2O 12. How is propanone prepared commercially? Give the reactions involved in it? Ans: Propanone is commercially prepared from cumene by its reaction with oxygen, followed by treating the product with dil. HCl CH2 CH3 | | CH3 – C – H + O2 CH3 – C – O – O - H | | C6H5 C6H5 Cumenc Cumene hydroperoxide CH3 | CH3 – C – O – O – H Dil HCl C6H5OH + CH3COCH3 | C6H5

3113. Give an example of an addition reaction of propanone? i) Addition with Hydrogen Cyanide (HCN) Ans:Propanone under go addition reaction with HCN to form propanone Cyanohydrin.

CH3 CH3 | | CH3 – C = O + HCN CH3 – C - OH | CN Propanone Propanone Cyanohydrin 14. How is ethanoic acid prepared commercially from methanol ? Ans: Ethanoic acid is prepared commercially by reaction between methanol and carbon monoxide in the presence of Iodine - rhodium catalyst. I2-Rh CH3OH + CO CH3COOH 15. Explain the follwing terms: i)Esterification ii)soponification(iii) decarbodylation (iv) Polymerisation Ans:Esterification:- The reaction of carboxylic acid with an alcohol to form ester in the presence of conc. H2SO4 know as Esterifilation reaction. CH3COOH + C2H5OH CH3COOC2H5 + H2O Saponification : oil or a fat on heating with sodium hydroxide (NaOH) Solution forms sodium salt of carboxylic acid (soap)and glycerol, this reaction is know as saponification reaction. CH2 – O COR CH2OH | | CH – O COR + 3NaOH CHOH + 3RCOONa | | CH2 – O COR CH2OH Decarboxylation: Sodium salt of ethanoic acid and soda lime on heating forms methane gas. This reaction is known as Decarboxylation reaction. CH3COONa + NaOH CH4 + Na2CO3 Polymerisation:The processes of formation of a big polymer from monomeric units is called as polymerization.

32 n CH2 = CH2 -CH2-[CH2-CH2]2-CH2- (Ethene) (polyethene) 16. Write chemical equations of the reactions of ethanoic acid with i)sodium (ii) sodium carbonates (iii) ethanol in presence of conc. H2SO4 and (iv) soda lime Ans: (i) 2 CH3COOH + 2Na 2CH3COONa + H2 (ii) 2CH3COOH + Na2CO3 2CH3COONa + CO2 + H2O (iii) CH3COOH + C2H5OH CH3COOC2H5 + H2O (iv) CH3COOH + NaOH CH4 + Na2CO3 17. What are polymers? How are they classified ? Ans: A polymer is a very big molecule formed by the combination of a large number of small molecules called monomers. Eg:- 1. Poly ethene 2. Poly vinyl chloride 3. Rubber 4. Nylon 5. Polyester Depending upon the type of chemical reaction involved in their preparation polymers are classified. Addition Polymers and Condensation polymers. addition polymers are obtained by the addition of unsaturated compounds (monomers) Catalyst n CH2 = CH2 (CH2 – CH2)n Δ n CH2 = CH Cl (CH2 – CH)n | Cl n CF2 = CF2 (CF2 – CF2)n n CH2 = CH2 (CH2 – CH2)n | | CH3 CH3 Condensation polymers Condensation polymers are obtained by the condensation of monomers in which monomer units are joined together with elimination of H2O,

33Eg: n HOOC – (CH2)6+ nH2N – (CH2)4COOH – NH2 [HN – (CH2)6-NHCO-(CH2)4-CO-NH]n + nH2O polyamide (Nylon-66) Eg:nHO-CH2-CH2-OH+ nHOOC-C6H4-COOH Ethylene Glycos Terphthalic acid

(O-CH2-CH2-O-CO-C6H4-Co)n+nH2O 19. Explain the term “vulcanization of rubbers”. What is the advantage of using vulcanized rubber over natural rubber? Ans: 01The process of heating natural rubber with sulphur to improve its property is called vulcanization of rubber. ADVANTAGES:- Natural rubber is very soft and sticky whereas vulcanized rubber is non-sticky and hard. Natural rubber has low tensile strength whereas vulcanized rubber has high tensile strength. Natural rubber has low elasticity whereas vulcanized rubber has high elasticity. Natural rubber absorbs more water where as vulcanized rubber absorbs very less water. Natural rubber has very low wear and tear resistances. Whereas vulcanized rubber has high wear and tear resistance. 18. Give two examples of polymers belonging to different classes. Ans:Addition polymers: Polyethene (CH2-CH2)n Polyvinylchloride (CH2-CH)n | cl

Teflon -(CF2 – CF2)n- Polypropene –(CH2-CH)2-

| CH3

Natural rubber (CH2-C=CH-CH2)

| CH3

Neoprene (CH2-C=CH-CH2)n Condensation Polymers: polyamide -(NH-(CH2)6-NHCO-(CH4)4-CO)-n

34(Nylon 66) Polyester -(O-CH2-CH2-OCO-CH4-CO-)n 20. Write the reactions involved in the formation of (i) Polyester and (ii) pOlyamide (I) polyester: nHO – (CH ) – CH – OH + nHOOC –C H – COOH 2 2 2 6 4 Ethylene glycol Terphthalic acid (O – CH – CH -OCO – C H –CO ) 2 2 6 4 polyester (Terylene)

n +nH2O

(ii) Polyamide: 553K nH=N – (CH2)6 – NH2 + – nHOOC-(CH2)4-COOH Hexamethylene diamine Acidic acid (-HNOC(CH2)4-CONH-(CH2)6)-NHCO-)n nylon 66 21) Explain the mechanism of the cleansing action of detergents Answer: Soaps has two parts 1) Long chain alkyl part 2)Ionic part COO-Na+

Ling chain alkyl Ionic / Polar (Hydrophobic) (Hydrophilic) water repelling water attracting When soaps is applied on only surface long chain alkyl part dissolves in oil particle to Micelle .In fact each micelle has negatively charged as shown below which are easily Washed away by water. Ref.Page No 199 Fig No. 15.2 of 10th Std. Science and Technology

35 22. Describe a method for preparation of soap Ans: Oil/fat is heated with Sodium hydroxide solution. In this process oil/fat is converted into glycerol and soap. This reaction is known as sopanication. Heat Oil/fat +Sodium hydroxide Soap + Glycerol CH2-OCOR CH2OH | | CH-OCOR + 3NaOH CHOH + 3RCOONa | | CH2-OCOR CH2OH When the soponification process is complete, somesodium chloride solution is added to solution to separate soap. Raw materials: i) Animal fat or vegetable oil ii) Sodium hydroxide iii) Sodium chloride