XI Chemistry - Karachi Board Numericals

Five Year Papers

1. Simplify according to the rule of significant figure .

2. The atomic mass of Zn is 65.4 a.m.u. Calculate (i) the number of moles and also the number of atoms in 10.9 gm of Zn. (ii) The mass of 1.204 x 1024 atoms of Zn in gm.

3. Adipic acid is used in the manufacture of Nylon. The acid contains 49.3%C, 6.9%H and 43.6%O by mass. The molecular mass of the acid is 146 a.m.u. Find the molecular formula of the Adipic Acid.

4. Calculate the value of R (Gas constant) with the help of Gas Equation when (i) the pressure is in atmosphere and the volume in dm3 or litre. (ii) the pressure is in Nm-2 and the volume is in cubic metre.

5. 400cm3 of helium gas effuse from a porous container in 20 seconds. How long will SO2 gas take to effuse from the same container? (Atomic Weight = S = 32, He = 4).

6. A system absorbs 200J of heat from the surroundings and does 120 J of work on the surroundings by expansions. Find the internal energy change of the system.

7. 1.2 gm of acetic acid (CH3COOH) is dissolved in water to make 200cm3 of the solution. Find the concentration of the solution in Molarity.

8. The solubility of calcium oxalate (CaC2O4) is 0.0016 g/dm3 at 25°C. Find the solubility product of calcium oxalate: CaC2O4 ® Ca2+ + C2O42-

9. Calculate H+ ion concentration of a solution whose pH = 5.6.

10. The rate constant (k) for the decomposition of nitrogen dioxide 2NO2(g) ® 2NO(g) + O2(g) is 1.8 x 103- dm3mole1-sec1-. Write down the rate expression and (i) find the initial rate when the initial concentration of NO2 is 0.75 M. (ii) Find the rate constant (k) when the initial concentration of NO2 is doubled.

11. Calculate the volume of nitrogen gas produced by heating 800 gm of ammonia at 21°C and 823 torr pressure. 2NH3 ® N2 + 3H2 (Atomic Weight = N = 14, H = 1)

12. In collection of 24 x 1025 molecules of C2H5OH. What is the number of moles. ( Atomic weight = C = 12, O = 16, H = 1)

13. Simplify using exponential notation: 43100 + 3900 + 2100.

14. A given compound contains 75. 2% carbon, 10.75% hydrogen and 14.05% oxygen. Calculate the empirical formula of the compound. (Atomic weight: C = 12, O = 16, H = 1)

15. Calculate the wave number of spectral line of hydrogen gas when an electron jumps from n = 4 to n= 2. (RH = 109678 cm-1)

16. 13.2 gm of gas occupies a volume of 0.918 dm3 at 25°C and 8 atm pressure. Calculate the molecular mass of the gas.

17. Calculate the heat of formation of benzene at 25°C when the heat of formation of CO2 and water and heat of combustion of benzene are given:

(i)


6C + 3H2 ® C6H6


DHf = ?

(ii)


C + O2 ® CO2


DH = -286KJ/mole

(iii)


H2 + ½O2 ® H2O


DH = -286KJ/mole

(iv)


C6H6 + 7.5O2 ® 6CO2 + 3H2O


DH = -3267 KJ/mole

18. The rate constant for the decomposition of nitrogen dioxide is 1.8 x 10-8 dm3 mole-1s-1. What is the initial rate when the initial concentration of NO2 is 0.50M? 2NO2 ® 2NO + O2.

19. Should AgCl precipitate from a solution prepared by mixing 400cm3 of 0.1M NaCl and 600cm3 of 0.03 M of solution of AgNO3? (Ksp for AgCl = 1.6 x 10-10 mole/dm3)

20. A sample of chlorine gas at S.T.P has a volume of 800cm3 calculate The number of moles of chlorine, the mass of the sample and the number of chlorine molecules in the sample.

21. How many atoms of carbon are present in 10 gm of coke?

22. The volume of the oxygen gas, collected over water at 24°C and 762mm pressure, is 128 ml. Calculate the mass in gm of oxygen gas obtained. The pressure of water vapour at 24°C is 22 mm.

23. Calculate the radius of orbit n = 3 for a Hydrogen atom in Armstrong unit. (h = 6.625 x 10-27 erg-sec, p = 3.14, m = 9.11 x 10-28gm, e = 4.8 x 10-10 esu)

24. For the reaction H2 + I2 ® 2HI. Kc is 49. Calculate the concentration of HI at equilibrium when initially one mole of H2 is mixed with one mole of I2 in one litre flask.

25. Determine the mass of HCl required to prepare 400 ml of 0.85M HCl solution.

26. Calculate pH value of 0.004M NaOH solution.

27. Kc for the reaction is 0.0194 and the calculated ratio of the concentration of the reactants and the product is 0.0116. Predict the direction of the reaction.

28. For the decomposition of ethyl chlorocarbonate ClCOOC2H5 ® CO2 + Cl.C2H5. Find the value of rate constant when initial concentration of Ethyl Chlorocarbonate is 0.25 M and the initial rate of the reaction is 3.25 x 10-4 mole/dm3/sec.

29. 1.0 gm of a sample of an organic substance was burnt in excess of oxygen yield 3.03 gm of CO2 and 1.55 gm of H2O. If the molecular mass of the compound is 58. Find the molecular formula.

30. Calculate the volume of the oxygen at S.T.P that may be obtained by complete decomposition of 51.3 gm of KClO3 on heating in presence of MnO2 as a catalyst. 2KClO3 ® 2KCl + 3O2. (Atomic mass of K = 39, Cl = 35.5, O = 16, Mn = 55)

31. Calculate the wave number of the Line in Lyman Series when an electron jumps from orbit 3 to orbit 1.

32. Calculate the heat of formation of ethane (C2H6) at 25°C from the following data:

(i)


2C + 3H2 ® C2H6


DHf = ?

(ii)


C + O2 ® CO2


DH = -394KJ/mole

(iii)


H2 + ½O2 ® H2O


DH = -286KJ/mole

(iv)


C2H6 + ½O2 ® 2CO2 + 3H2O


DH = -1560.632KJ/mole

33. At the equilibrium a 12 litre flask contains 0.21 mole of PCl5, 0.32 mole of Cl2 at 250°C. Find the value of Kc for the reaction. PCl5 Û PCl3 + Cl2.

34. A given compound contains C = 60%, H = 13.0% and O = 27%. Calculate its Empirical Formula.

35. How many grams of chlorine are required to prepare 7.75 dm3 of chloro benzene? The equation of the reaction is C6H6 + Cl2 ® C6H5Cl + HCl. (Atomic Number of C = 12, H = 1 and Cl = 35.5)

36. A mixture of helium and hydrogen is confined in a 12 dm3 flask at 30°C. If 0.2 mole of the helium is present, find out the partial pressure of each gas whereas the pressure of the mixture of gases is 2atm.

37. Calculate the radius by hydrogen atom by applying Bohr’s Theory. (h = 6.625 x 10-27 erg-sec, p = 3.14, m = 9.11 x 10-28gm, e = 4.8 x 10-10 esu)

38. Calculate the heat of formation of C2H2 from carbon and hydrogen from the following data:

(i)


2C + H2 ® C2H2


DHf = ?

(ii)


C + O2 ® CO2


DH = -94.05Kcal/mole

(iii)


H2 + ½O2 ® H2O


DH = -68.32Kcal/mole

(iv)


C2H2 + 5/2O2 ® 2CO2 + H2O


DH = -310Kcal/mole

39. Calculate the pH of a 2.356 x 10-3m HCl solution.

40. For the reaction N2 + 3H2 Û 2NH3. The equilibrium mixture contains 0.25 M nitrogen, 0.15M hydrogen gas at 25°C. Calculate the concentration of NH3 gas when Kc = 9.6. the volume of the container is 1dm3.

41. Determine the initial rate of the following reaction at 303°C in which its rate constant is 8.5 x 10-5 litre-mol-1 sec-1. Initial concentration of the reaction is 9.8 x 10-2 mole/litre. 2NO2 ® 2NO + O2.

Extra Numericals

1. 4.6gm of ethyl alcohol and 6.0gm of acetic acid kept at constant temperature until equilibrium was established. 2 gm of acid were present unused. Calculate Kc.

2. Kc for the dissociation of HI at 350°C is 0.01. If 0.2 mole of H2, 1.3 moles of I2 and 4 moles of HI are present. Predict the direction of reaction.

3. What is the solubility of PbCrO4 at 30°C when Ksp is 1.8 x 10-14.

4. 1.06m of an organic compound on combustion gave 1.49 gm of CO2 and 0.763gm H2O. It also has 23.73% N. Find its compercial formula.

5. 500 dm3 of moist O2 gas was collected over water at 27°C and 726torr pressure. Find the mass in gm. Of dry O2 gas at S.T.P. When the vapour pressure of water 27°C is 26 torr.

6. Atomic mass of phosphorus is 31. Calculate the mass of 45 atoms in a.m.u.

7. Methane burn in steam according the following reaction: CH4 + 2O2 ® CO2 + 2H2O. If 100 gm of each CH4 and O2 is taken, then what amount of CO2 liberated?

8. An organic compound containing C = 65.45%, H = 5.45% and O = 29.09%. If molecular weight of compound is 110, calculate molecular formula.

9. What mass of CO2 is produced by the complete combustion of 100g pentane. C5H12 + 3O2 ® 2CO2 + 2H2O.

10. One atom of an unknown element is found to have a mass of 67.8 x 10-23g. What is the atomic weight of the element?

11. The heat of combustion of glucose and alcohol is given below.

(i)


C6H12O6 + 6O2 ® 6CO2 + 6H2O


DH = -673Kcal/mole

(ii)


C2H5OH+ 3O2 ® 2CO2 + 3H2O


DH = -328Kcal/mole

Find DH for the fermentation given below:





C6H12O6 ® 2C2H5OH + 3CO2





12. At certain temperature, the equilibrium mixture contain 0.4 mole of H2, 0.4mole I2 and 1 mole of HI. If addition 2 mole of H2 are added. How many moles of HI will be present when the new equilibrium established. H2 + I2 ® 2HI.

13. A solution has pH of 8.4. Find concentration of H+ and OH-.

14. 180cm3 of a known gas diffuse in 15minutes, when 120 cm3 of SO2 diffuses in 20 minutes. What is the molecular mass of the unknown gas.

Chapter 1

Introduction to Fundamental Concepts

1. Calculate the moles of the following in 500gm, NH3, HCl, Na2CO3, H2SO4, MgBr2, CaCO3, Xe and C.

2. How many moles of Na are present in 5gm of Na?

3. Calculate the number of atoms in 12 gms of Mg.

4. 2gm diamond is studded in a ring. Diamond is a pure carbon. How many atoms of carbon are present in the ring?

5. Calculate the number of molecules in 9gms of H2O.

6. How many molecules are present in 25 gms of CaCO3?

7. Calculate the weight in gram of 3.01 x 1020 molecules of glucose (C6H12O6)

8. How many atoms of hydrogen are there in 2.57 x 10-6 gram of hydrogen?

9. A sample of oxygen contains 1.87 x 1027 atoms of oxygen. What would be the weight of the oxygen?

10. Find the weight of oxygen obtained from 49gm of KClO3.

2KClO3 ® 2KCl + 3O2

11. What weight of CO2 and CaO can be obtained by heating 12.5gm of Limestone (CaCO2)?

CaCO3 ® CaO + CO2

12. Calculate the weight of sodium chloride required to produce 142 gm of chlorine.

2NaCl ® 2Na + Cl2

13. Calculate the weight of carbon, required to produce 88gm of CO2.

C + O2 ® CO2

14. The action of CO on Fe2O3 can be represented by the following equation.

Fe2O3 + 3CO ® 2Fe + 3CO2

15. What weight of NH3 will be required to produce 100 gm of NO?

4NH3 + 5O2 ® 4NO + 6H2O

16. Find out the moles of CuSO4 which are obtained from 31.75 gm of Cu.

Cu + H2SO2 ® CuSO2 + H2

17. Calculate the number of N2 and H2 molecules, which are obtained from 8.5 gm of NH3.

N2 + 3H2 ® 2NH3

18. Find out the number of Cu and H2O molecules obtained from 7.95gm of CuO.

CuO + H2 ® Cu + H2O

19. 400gm of H2 was made to combine with 14200gm of Cl2. How much HCl will be produced?

20. 1kg of Limestone was heated 500gm of CaO was obtained. How much CO2 gas produced into air.

21. Find the weight of O2 obtained from 49 gm of KClO3.

2KClO3 ® 2KCl + 3O2

22. Chlorine is produced on the large scale by the electrolysis of NaCl aqueous solution. Chlorine the weight of NaCl required to produce 142 gm of Cl2.

2NaCl + 2H2O ® Cl2 + H2 + 2NaOH

23. How many grams of O2 are required to completely burn 18.0gm of C? How many grams of CO2 will be formed?

24. Calculate the weight of NH3, required to produce 100 gms of NO.

4NH3 + 5O2 ® 4NO + 6H2O

25. Find out the moles of H2 and N2 required producing 17gm of NH3.

26. Calculate the volume of H2 at S.T.P, which is obtained by the reaction of 120 gm Mg with MgSO4.

Mg + H2SO4 ® MgSO2 + H2

27. NH3 gas can be produced from ammonium chloride (NH4Cl) as follows:

CaO + 2NH4Cl ® CaCl2 + H2O + NH3

Calculate the volume of NH3 obtained at S.T.P by the reaction of 100 gm of NH4Cl.

28. 500gm of C2H4 on combustion in air gave CO2 and H2O. Calculate the volume of O2 and CO2 at S.T.P.

29. Find out the volume of O2, CO2 and SO2 gases at S.T.P react and obtained from 2 moles of CS2.

CS2 + 3O2 ® CO2 + 2SO2

30. Calculate the volume of CO2 gas at S.T.P obtained by the combustion of 20gm of CH4.

CH4 + 2O2 ® CO2 + 2H2O

31. Calculate the volume of O2 gas at S.T.P required to burn 600dm3 of H2S, also find the volume of SO2 gas produced at S.T.P.

32. Calculate the volume of O2 gas at S.T.P required to burn 50 gm of CH4.

33. What volume of H2 at S.T.P can be produced by the reaction of 6.54gm Zn with HCl?

Zn + 2HCl ® ZnCl2 + 2H2

34. Calculate the volume of O2 and H2 gases at S.T.P obtained from 9gm of H2O.

35. 0.264gm of Mg was burnt in pure O2. How much MgO will be formed?

2Mg + O2 ® 2MgO

36. How much H2 can be generated by passing 200gm of steam over hot iron.

4H2O + 3Fe ® Fe3O4 + 4H2

37. If 112dm3 of N2 react with 336 dm3 of H2, both at S.T.P. How many grams of NH3 would be obtained?

N2 + 3H2 ® 2NH3

38. An organic compound contains 12.8%C, 2.1% and 85.1% Br. If the mass of the compound is 188, find the molecular formula.

39. An organic compound contains 66.70%C, 7.41% H and 25.90% N2. The molecular mass of the compound is 108. Find out its molecular formula.

40. A compound contains 19.8%C, 2.5%H, 66.1%O and 11.6%N. Find out empirical formula of the compound.

41. 0.2475gm of a compound, containing C, H and O gave 0.4950gm CO2 and 0.2025gm H2O. If the molecular mass of the compound is 88. Find out the molecular formula.

42. An organic compound contains 32%C, 6.67%H, 18.66%N and 42.67%O. Its molecular mass is 75. Find out the molecular formula of the compound.

43. 1.367gm of a compound containing C, H and O on heating gave 3.002gm CO2 and 1.640gm H2O. Find out its molecular formula, when the molecular mass is 120.

44. A compound was found to contain 40%C and 6.7%H. Its molecular mass was 60. Find out its molecular formula.

45. An organic compound contains 75.2%C, 10.15%H and oxygen. Its molecular mass is 115. Find its molecular formula.

46. The empirical formula of a compound is CH2O. If the molecular mass 180. Find out the molecular formula.

47. An organic compound composed of C, H and O. On combustion of 0.94gm of this compound, 1.32gm CO2 and 0.568gm H2O were obtained. Its molecular mass is 180. Find its molecular formula.

48. An organic compound composed of C, H and O. 4.2gm of the compound on heating gave 6.21gm CO2 and 2.54gmH2O. Its molecular mass is 60. Find its molecular formula.

49. An organic compound contains C,H and 6.38gm of compound on combustion gave 9.06gm CO2 and 5.58gm H2O. Its molecular mass is 62. Find out its molecular formula.

50. 1gm of a hydrocarbon on combustion gave 3.03gm of CO2 and 1.55gm of H2O. If the molecular mass is 58, find its molecular formula.

51. 1.434gm of a compound on combustion gave 4.444gm CO2 and 2.0 gm H2O. Find out its empirical formula.

52. An organic compound composed of C, H and N. 0.225gm of compound on combustion gave 0.44gm CO2 and 0.315gm H2O. If the molecular mass of a compound is 90, find out its molecular formula.

53. An organic compound contains 40.68%C, 8.47%H, 23.73%N and 27.12%O. Find its empirical formula.

54. An organic compound composed of C, H and N. 0.419 gm of compound on combustion gave 0.88gm CO2 and 0.27gm H2O. Find out its empirical formula.

55. The analysis of a compound shows, C = 24.24%, H = 4.04% and Cl = 71.71%. If the molecular mass of the compound is 49.5, find its molecular formula.

56. An organic compound of molecular mass 90 has the empirical formula CH2O. What is its molecular formula?

57. The empirical formula of an organic compound is CH3NO2. If it’s molecular mass is 61. What is its molecular formula?

58. 0.638gm of an organic compound on combustion gave 0.594gm H2O and 1.452gm CO2.The compound is composed of C, H and O atoms. If the molecular mass is 116, find out its molecular formula.

59. The molecular formula of ethyl acetate is CH3COOC2H5. What is its empirical formula.

60. Find the empirical formulae of the following compounds from their percentage composition by mass:

· N = 26.17% H = 7.48% Cl = 66.35%

· Ca = 71.43% O = 28.57%

· Ag = 63.53% N = 8.23% O = 28.24%

· Na = 32.40% H = 45.07% Cl = 22.53%

61. A certain compound on analysis yielded 2.00gm C, 0.34gm H and 2.67gm O. If the relative molecular mass of the compound is 60, calculate its molecular formula.

62. What is the empirical formula of a compound, which contains 42.5% chlorine and 57.5 oxygen. If it’s formula mass is 167. What is its molecular formula?

63. What will be the weight of 5 moles of water in grams?

64. What is the mass of each of the following:

· 1.25 mole of NaCl

· 2.42 mole of NaNO3

· 1.5 mole of HCl

· 3.0 mole of NaOH

65. A piece of Aluminium metal weighs 70.0g. How many atoms are present in the piece.

66. How many atoms of carbon are present in 20-carat Diamond? (1 carat = 0.2g)

67. How many grams of oxygen have the same number of atoms as 16gm of sulphur?

68. A sample of oxygen gas at STP has a mass of 16gm. Calculate:

· The number of moles of oxygen

· The volume of the sample

· The number o molecules in the sample

69. Calculate the volume of CH4 gas at STP having a mass 32g.

70. What mass of zinc sulphate can be obtained from the reaction of 10.0gm of Zinc with an excess of dilute H2SO4?

Zn + H2SO4 ® ZnSO4 + H2­

71. Calculate what mass of sodium hydroxide you would need to neutralize a solution containing 7.3g hydrogen chloride by the reaction:

NaOH + HCl ® NaCl + H2O

72. Calculate how much sodium nitrate you need to give 126g of nitric acid by the reaction:

NaNO3 + H2SO4 ® HNO3 + NaHSO4

73. What volume of hydrogen at STP is evolved when 0.325g of zinc reacts will dilute hydrochloric acid.

Zn + 2HCl ® ZnCl2 + H2

74. What mass of oxygen is formed by the decomposition of a solution containing 120cm3 of H2O2 at STP?

2H2O2 ® 2H2O + O2

75. What is the mass of one molecule of water in grams?

76. 100cm3 of butane are burned in an excess of oxygen. Calculate:

· The volume of oxygen used

· The mass and volume of CO2 produced (assume all gases at STP)

2C4H10 + 13O2 ® 8CO2 + 10H2O

77. A cook is making a small cake. It needs 500cm3 at STP of CO2 to make the cake rise. The cook decides to add baking powder, which contains sodium bicarbonate. This generates CO2 by thermal decomposition.

2NaHCO3 ® CO2 + Na2CO3 + H2O

What mass of baking powder must the cook add to cake mixture?

78. What volume of ammonia at STP can be obtained by heating 0.25 mole of ammonium sulphate with calcium hydroxide?

(NH4)SO4 + Ca(OH)2 ® 2NH3 + CaSO4 + 2H2O

79. How many grams of SO2 are produced when 100g of H2S is reacted with 50g of oxygen.

2H2S + 3O2 ® 2H2O + 2SO2

80. How many grams of chlorobenzene will be produced when 100gm of each reactant is reacted?

C6H6 + Cl2 ® C6H5Cl + HCl

81. A car releases about 5g of NO into the air for each mile driven. How many molecules of NO are emitted per mile?

82. Simplify according to the rule of significant figures.

· 2.60 x 3.05

· 0.009 ¸ 0.3

·

·

Chapter 2

The Three States of Matter

1. 540cm3 of N2 at 400mm pressure are compressed to 300cm3 without changing the temperature. What will be the pressure of the gas?

2. A gas occupies 6dm3 at 1atm pressure keeping the temperature constant. If the pressure reduces to 600mm, what volume does the gas occupy?

3. At a certain temperature and 800mm pressure, the volume of H2 is 700cm3. If the pressure is increased to 1000mm at the same temperature, find the new volume of the gas.

4. 150ml of a gas at 27°C is heated to 77°C at constant pressure. Find the new volume of the gas.

5. 300ml of N2 are at 50° and the pressure is kept constant. If the temperature is doubled, what will be the volume of the gas?

6. A gas measures 5dm3 at 5°C under 0.5atm pressure. Calculate its volume at 25° and 5000mm pressure.

7. 2060ml of a gas is at 7°C and 860mm pressure. Find its volume at S.T,P.

8. 350ml of H2 was collected over water at 26°C. The pressure of the gas was 900mm. What volume will dry gas have at 30°C and 750mm pressure? The vapour pressure at 26°C is 25mm.

9. The volume of oxygen collected over water at 20°C and 1200mm pressure, is 200cm3. If aqueous at 20°C is 17.4mm, what will be the volume of the gas under S.T.P.

10. A 20dm3 flask contains H2 at 22°C under pressure of 1.2 atm. How many moles of H2 are present.

11. A gaseous mixture is at the pressure of 3000mm. The mixture contains 6 moles of N2, 0.5mole of CO2 and 2.5 moles of O2. Find the partial pressure of each gas.

12. A 5dm3 vessel contains 1.2 moles of H2 and 0.8 mole of N2 at 27°C. Find the total pressure of the mixture.

13. Composition of a sample of air by volume is, N2 = 76%, O2 = 20%, H2O = 2.5%, CO2 = 1.4% and He = 0.1%. If the pressure of the air is 760 mm, Calculate the partial pressure of these gases.

14. A 10dm3 container contains a mixture of He and Ne gases at 17°C. There are two moles of He gas and 3 moles of Ne gas. What is the partial pressure of the gases?

15. 10gm of H2, 96gm of O2 and 196gm of N2 are mixed together. The partial pressure of H2 is 0.6 atm. What is the partial pressure of O2 and N2?

16. A cylinder contains 1 mole of H2, 3 mole of He and 6 moles of N2. The total pressure in the cylinder is 15 atm. Calculate the partial pressure of H2, He and N2.

Chapter 5

Energetics of Chemical Reaction

1. Calculate the heat of formation of Acetic Acid from the following data:

(i)


2C + 2H2+ O2 ® CH3COOH


DHf = ?

(ii)


C + O2 ® CO2


DH = -394KJ/mole

(iii)


H2 + ½O2 ® H2O


DH = -286 KJ/mole

(iv)


CH3COOH + 2O2 ® 2CO2 + 2H2O


DH = -870KJ/mole

2. Calculate the heat of formation of Ethane from the following data:

(i)


2C + 3H2 ® C2H6


DHf = ?

(ii)


C + O2 ® CO2


DH = -394KJ/mole

(iii)


H2 + ½O2 ® H2O


DH = -286 KJ/mole

(iv)


C2H6 + 7/2O2 ® 2CO2 + 3H2O


DH = -1560KJ/mole

(v)


C2H5OH + 3O2 ® 2CO2 + 3H2O


DH = -327 KJ/mole

3. Calculate the heat of formation of Methane from the following data:

(i)


C + 2H2 ® CH4


DHf = ?

(ii)


C + O2 ® CO2


DH = -394KJ/mole

(iii)


H2 + ½O2 ® H2O


DH = -286 KJ/mole

(iv)


CH4 + 2O2 ® CO2 + 2H2O


DH = -890.3KJ/mole

4. Calculate the heat of formation of Ethyl Alcohol from the following data:

(i)


2C + 3H2 ½ O2® C2H5OH


DHf = ?

(ii)


C + O2 ® CO2


DH = -394KJ/mole

(iii)


H2 + ½O2 ® H2O


DH = -286 KJ/mole

(iv)


C2H5OH+ 3O2 ® 2CO2 + 3H2O


DH = -1369KJ/mole

5. Calculate the heat of formation of Ethane from the following data:

(i)


C2H6 + 7/2O2 ® 2CO2 + 3H2O


DHf = ?

(ii)


C + O2 ® CO2


DH = -394KJ/mole

(iii)


H2 + ½O2 ® H2O


DH = -286 KJ/mole

(iv)


C2H6 ® 2C + 3H2


DH = -84.68KJ/mole

6. Calculate the heat of formation of Methane from the following data:

(i)


C + 2H2 ® CH4


DHf = ?

(ii)


C + O2 ® CO2


DH = -94.1cal

(iii)


H2 + ½O2 ® H2O


DH = -68.3 cal

(iv)


CH4 + 2O2 ® CO2 + 2H2O


DH = -212.8 cal

7. Calculate the heat of formation of Ethene from the following data:

(i)


2C + 2H2 ® C2H4


DHf = ?

(ii)


C + O2 ® CO2


DH = -97kcal

(iii)


H2 + ½O2 ® H2O


DH = -65 kcal

(iv)


C2H4 + 3O2® 2CO2 + 2H2O


DH = 340 kcal

8. Calculate the heat of formation from the following data:

(i)


2C + 3H2 +1/2O2 ® C2H5O


DHf = ?

(ii)


C + O2 ® CO2


DH = -94.2Kcal/mole

(iii)


H2 + ½O2 ® H2O


DH = -68.5 Kcal/mole

9. Calculate the heat of formation of from the following data:

(i)


C + 2H2 + O2® CH3OH


DHf = ?

(ii)


C + O2 ® CO2


DH = -94.2Kcal/mole

(iii)


H2 + ½O2 ® H2O


DH = -68.32 Kcal/mole

(iv)


CH3OH + O2 ® CO2 + 2H2O


DH = -347.6Kcal/mole

10. Calculate the heat of formation of from the following data:

(i)


3C + 4H2 ® C3H8


DHf = ?

(ii)


C + O2 ® CO2


DH = -94.1Kcal/mole

(iii)


H2 + ½O2 ® H2O


DH = -68.3 Kcal/mole

(iv)


C3H8 + 5O2 ® 3CO2 + 4H2O


DH = -530.7Kcal/mole

11. Calculate the heat of formation of from the following data:

(i)


H2 + O2® H2O2


DHf = ?

(ii)


H2 + ½O2 ® H2O


DH = -68.32Kcal

(iii)


H2O + ½ O2 ® H2O2


DH = -23.48Kcal

12. Given:

(i)


NH3 + HCl ® NH4Cl


DH1 = 42.100Kcal

(ii)


H2O + ½ O2 ® H2O2


DH2 = 3.900cal

Find DH for the reaction,





NH3 + HCl ® NH4Cl


DHf = ?

Chapter 6

Chemical Equilibrium

1. 1.5 moles of acetic acid and 1.5 moles of ethyl alcohol were reacted at a certain temperature. At equilibrium, 1 mole of ethyl acetate was present in 1 litre of the equilibrium mixture. Calculate the equilibrium constant Kc.

CH3COOH + C2H5OH Û CH3COOC2H5 + H2O

2. 6.0 gm of hydrogen and 1016gm of iodine were heated in a sealed tube at a temperature, at which Kc is 50. The volume of the tube is 1 dm3. Calculate the concentration of HI.

H2 + I2 Û 2HI

3. At a certain temperature, an equilibrium mixture contains 0.4 mole H2, 0.4 mole I2 and 1 mole of HI. The volume of the reacting vessel is 4 dm3. Find out the equilibrium constant kc.

H2 + I2 Û 2HI

4. 3 moles of A and 2 moles of B are mixed in a 4dm3 flask, at a certain temperature. The following reaction occurs.

3A + 2B Û 4C

At equilibrium the flask contains 1 mole of B. Find the equilibrium constant kc.

5. At a certain temperature, 0.205 mole of H2 and 0.319 mole of I2 were reacted. The equilibrium mixture contains 0.314 mole of I2. Calculate the kc.

H2 + I2 Û 2HI

6. The kc for the reaction A + B Û C + D is 1/3. How many moles of A must be mixed with 3 moles of B to yield at equilibrium, 2 moles of C and D each. The volume of the vessel is 2 litre.

7. At a certain temperature the equilibrium mixture for the reaction A + B Û 2C, contains 2 moles A, 3 moles of B and 5 moles of C. Find the Kc for the reaction.

8. For the reaction 2A Û B + C, equilibrium constant kc is 1. If we start with 6 moles of A, how many moles of B will be formed.

9. 20 moles of SO2 and 10 moles of O2 are taken in a 20 litre flask. If at equilibrium 5 moles of SO3 are formed, Calculate kc.

2SO2 + O2 Û 2SO3

10. A quantity of PCl5 was heated in a 12 dm3 vessel at 250°C.

PCl5 Û PCl3 + Cl2

11. 2 moles of HI was introduced in a vessel held at constant temperature. When equilibrium was reached, it was found that 0.1 mole of I2 have been formed. Calculate the equilibrium constant.

H2 + I2 Û 2HI

12. When 1 mole of pure C2H5OH is mixed with 1 mole of CH3COOH at room temperature, the equilibrium mixture contains 2/3 moles of ester and water each.

· What will be the kc?

· How many moles of ester are formed at equilibrium when 3 moles of C2H5OH are mixed with 1 mole of CH3COOH?

CH3COOH + C2H5OH Û CH3COOC2H5 + H2O

13. PCl5 Û PCl3 + Cl2. Calculate the number of moles of Cl2 produced at equilibrium when 1 mole of PCl5 is heated at 250°C in a vessel having capacity of 10dm3. At 250°C, Kc is 0.041.

14. When 2.94 moles of iodine and 8.1 moles of Hydrogen were mixed and heated at 444°C and at constant volume, until the equilibrium was established. 5.64 moles of HI were formed. Calculate the value of kc.

H2 + I2 Û 2HI

15. What is the solubility of lead chromate in moles/dm3 at 25°C. The solubility product is 1.8 x 10-14.

PbCrO4 Û Pb++ + CrO4--

16. The solubility of Mg(OH)2 at 25°C is 0.00764 gm/dm3. What is the solubility product of Mg(OH)2?

Mg(OH)2 Û Mg++ + 2OH-

17. Find the solubility of AgCl in gm/dm3, when the solubility product is 1.25 x 10-10.

18. Calculate the solubility product of BaSO4. The solubility of the salt is 1.0 x 10-5 moles/dm3.

19. Calculate the solubility product of BaSO4 is 9.0 x 10-3 gm/dm3. Find its solubility product.

20. Predict whether there will be any precipitate formation by mixing 30cm3 of 0.01M NaCl with 60cm3 of 0.01M AgNO3 solution. Ksp of AgCl is 1.5 x 10-10.

21. A saturated solution of calcium fluoride was found to contain 0.0168 gm/dm3 of solute at 25°C. Calculate the ksp for CaF2.

22. A saturated solution of BaF2 at 25°C is 0.006M. Calculate Ksp of the salt.