Mc Ques Eng H2so4 So2

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Sulphuric acid and Sulphur dioxide Public Exam Questions :

1. Concentrated sulphuric acid turns blue litmus paper red and then black. On the basis of these colour changes, which of the following deductions concerning concentrated sulphuric acid are correct? (1) It contains H+(aq) ions. (2) It is an oxidizing agent. (3) It is a dehydrating agent. A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) (HKCEE 1994)

2. 1st statement : At room temperature and pressure, the molar volume of oxygen gas is greater than that of hydrogen gas. nd 2 statement : The relative atomic mass of oxygen is greater than that of hydrogen. (HKCEE 1994)

3. The reaction of cane sugar and concentrated sulphuric acid may be represented by the following equation.

In this reaction, concentrated sulphuric acid acts as A. a strong acid. B. an oxidizing agent. C. a drying agent. D. a dehydrating agent. (HKCEE 1995)

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4. Refer to the following chemical equation : Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g) What volume of carbon dioxide, measured at room temperature and pressure, is produced if 224g of iron are formed? (relative atomic mass : Fe = 56; Molar volume of gas at room temperature and pressure = 24 dm3) A. 16 dm3 B. 36 dm3 C. 72 dm3 D. 144 dm3 (HKCEE 1995)

5. Which of the following statements concerning the Contact Process is/are correct? (1) The sulphur dioxide used in the process can be produced by roasting sulphide ores. (2) A gaseous mixture of sulphur dioxide and oxygen in the mole ratio of 1 : 2 is passed into the catalytic conversion chamber. (3) The sulphur trioxide produced is absorbed by water in the absorption tower. A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only (HKCEE 1995)

6. Which of the following experiments can be used to show that concentrated sulphuric acid is a dehydrating agent? A. adding it to copper(II) oxide powder B. adding it to copper(II) sulphate crystals C. adding it to calcium carbonate powder D. adding it to sodium chloride crystals (HKCEE 1996)

7. In an experiment, 1.6g of sulphur are burnt completely in air to form sulphur dioxide. What volume of sulphur dioxide, measured at room temperature and pressure, is formed? (Relative atomic mass : S = 32.0; Molar volume of gas at room temperature and pressure = 24.0 dm3) A. 0.6 dm3 B. 1.2 dm3 C. 2.4 dm3 D. 12.0 dm3 -2-

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8. One mole of each of the following compounds is burnt completely in oxygen. Which compound requires the greatest volume of oxygen, measured at room temperature and pressure, for complete combustion? A. carbon monoxide B. ethane C. ethene D. ethanol (HKCEE 1996)

9. Under certain conditions, 60cm3 of a gaseous compound, NxOy, decompose completely to give 60cm3 of nitrogen gas and 30cm3 of oxygen gas. (All gas volumes are measured at the same temperature and pressure.) Which of the following combinations is correct? x y A. 1 1 B. 1 2 C. 2 1 D. 2 3 (HKCEE 1996)

10. Which of the following statements concerning one mole of nitrogen gas is/are correct? (1) It has a mass of 14.0g. (2) It occupies the same volume as 4.0g of helium gas at room temperature and pressure. (3) It contains 6.02 × 1023 atoms of nitrogen. (Relative atomic masses : He = 4.0; N = 14.0; Avogadro constant = 6.02 × 1023 mol-1) A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only (HKCEE 1996)

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11. In which of the following reactions does sulphur dioxide act as a reducing agent? (1) the production of sulphuric acid in the Contact Process (2) the bleaching of a red petal (3) the decolourization of bromine water A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) (HKCEE 1996)

12. The atomic number of element X is 16. Which of the following statements concerning X are correct? (1) X can react with calcium to form an ionic compound. (2) The oxide of X dissolves in water to form an acidic solution. (3) X can conduct electricity in its molten state. A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) (HKCEE 1996)

13. 1st statement : The volume of hydrogen liberated at room temperature and pressure by the reaction between 10cm3 of 10M hydrochloric acid and excess zinc granules is greater than that between 50cm3 of 2M hydrochloric acid and excess zinc granules. 2nd statement : 10M hydrochloric acid is a stronger acid than 2M hydrochloric acid. (HKCEE 1996)

14. Which of the following gases occupies the largest volume at room temperature and pressure? (Relative atomic masses : H = 1.0; C = 12.0; N = 14.0; O = 16.0; Molar volume of gas at room temperature and pressure = 24.0 dm3) A. 1.0g of ammonia B. 2.0g of nitrogen C. 3.0g of oxygen D. 4.0g of carbon dioxide (HKCEE 1997)

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15. An iron nail is heated with concentrated sulphuric acid. Which of the following combinations is correct? Gas given off Colour of solution formed A. hydrogen pale green B. hydrogen yellow C. sulphur dioxide pale green D. sulphur dioxide yellow (HKCEE 1997)

16. One mole of sulphur atoms has a mass twice that of one mole of oxygen atoms. Which of the following statements is/are correct? (1) 2g of sulphur and 1g of oxygen each occupy the same volume at room temperature and pressure. (2) 2g of sulphur and 1g of oxygen each contain the same number of atoms. (3) The number of atoms contained in one mole of sulphur is twice that contained in one mole of oxygen. A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only (HKCEE 1997)

17. Concentrated sulphuric acid is corrosive to skin because (1) it is a dehydrating agent. (2) it is an oxidizing agent. (3) each molecule of sulphuric acid has two ionizable hydrogen atoms. Which of the above statements are correct? A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) (HKCEE 1997)

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18. 7.5g of calcium carbonate is added to 50.0cm3 of 2M hydrochloric acid. What is the volume of carbon dioxide liberated at room temperature and pressure? (Relative atomic masses : C= 12.0; O = 16.0; Ca = 40.0; Molar volume of gas at room temperature and pressure = 24.0 dm3) A. 0.9 dm3 B. 1.2 dm3 C. 1.8 dm3 D. 2.4 dm3 (HKCEE 1998)

19. Which of the following experiments would produce sulphur dioxide? (1) heating iron pyrites in air (2) heating a mixture of iron and dilute sulphuric acid (3) heating a mixture of copper and concentrated sulphuric acid A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) (HKCEE 1998)

20. 1st statement : One mole of water occupies the same volume as one mole of carbon dioxide at room temperature and pressure. nd 2 statement : One mole of water contains the same number of atoms as one mole of carbon dioxide. (HKCEE 1998)

21. Substance X gives identical product(s) when treated with dilute sulphuric acid or concentrated sulphuric acid. X may be A. zinc. B. cane sugar. C. ammonia. D. hydrated copper(II) sulphate crystals. (HKCEE 1999)

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22. In an experiment, sulphur dioxide is passed into an iodine solution which is prepared by dissolving some iodine in potassium iodide solution. Which of the following statements concerning this experiment is correct? A. The colour of iodine solution changes from purple to colourless. B. A brown solid is formed. C. A displacement reaction occurs. D. Sulphur dioxide is oxidized to sulphate ions. (HKCEE 1999)

23. In an experiment, 21.8g of zinc was treated with 250.0cm 3 of 2.0M hydrochloric acid. What volume of hydrogen was liberated at room temperature and pressure? (Relative atomic mass : Zn = 65.4; Molar volume of gas at room temperature and pressure = 24.0 dm3) A. 4.0 dm3 B. 6.0 dm3 C. 8.0 dm3 D. 12.0 dm3 (HKCEE 2000)

24. Which of the following statements concerning sulphur dioxide are correct? (1) It can be prepared by heating copper turnings with concentrated sulphuric acid. (2) It is denser than air. (3) It can be absorbed by sodium hydroxide solution. A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) (HKCEE 2000)

25. 1st statement : Concentrated sulphuric acid can turn a piece of filter paper black. 2nd statement : Concentrated sulphuric acid is a strong oxidizing agent. (HKCEE 2000)

26. 1st statement : The volume of 10.0g of gaseous carbon dioxide is the same as the volume of 10.0g of solid carbon dioxide. 2nd statement : 10.0g of gaseous carbon dioxide contains the same number of molecules as 10.0g of solid carbon dioxide. (HKCEE 2000)

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27. Consider the reaction : 4H2(g) + Fe3O4(s) → 3Fe(s) + 4H2O(l) What mass of iron would be obtained if 96.0 cm3 of hydrogen, measured at room temperature and pressure, is consumed in the reaction? (Relative atomic mass : Fe = 56.0; Molar volume of gas at room temperature and pressure = 4.0 dm3) A. 0.056 kg B. 0.084 kg C. 0.168 kg D. 0.224 kg (HKCEE 2001)

28. Suppose that the Avogadro number is L. How many atoms does 600 cm3 of oxygen at room temperature and pressure contain? (Molar volume of gas at room temperature and pressure = 24.0 dm3) 1 A. 40 L 1 B. 20 L C. 25L D. 50L (HKCEE 2001)

29. Consider the information below about the reaction of hydrogen with chlorine : H2(g) + Cl2(g) → 2HCl(g)

∆H < 0

Which of the following statements can be deduced from the above information? (1) Heat is liberated when hydrogen chloride is formed. (2) Hydrogen and chlorine react at room temperature. (3) When measured at room temperature and pressure, the total gas volume before the reaction equals that after the reaction. A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only (HKCEE 2001) -8-

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30. Which of the following are correct descriptions of the uses of sulphuric acid? (1) treatment of metal surfaces in the electroplating industry (2) manufacture of paint additives (3) manufacture of fertilizers A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) (HKCEE 2001)

31. 1st statement : Bromine water can be used to distinguish between sodium sulphate solution and sodium sulphite solution. nd 2 statement : Bromine can be reduced by sodium sulphite to colourless bromide ions, but not by sodium sulphate. (HKCEE 2001)

32. Gases X and Y react to give a gaseous product Z. The reaction can be represented by the equation : X(g) + 3Y(g) → 2Z(g) In an experiment, 40 cm3 of X and 60 cm3 of Y are mixed and are allowed to react in a closed vessel. What is the volume of the resultant gaseous mixture? (All volumes are measured at room temperature and pressure.) A. 40 cm3 B. 60 cm3 C. 80 cm3 D. 100 cm3 (HKCEE 2002)

33. Which of the following gases contains the greatest number of molecules at room temperature and pressure? (Relative atomic masses : H = 1.0; N = 14.0; O = 16.0; Cl = 35.5) A. 2.0g of hydrogen B. 16.0g of oxygen C. 18.0g of ammonia D. 60.0g of chlorine (HKCEE 2002)

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34. Starch, a natural polymer, is a carbohydrate. When concentrated sulphuric acid is added dropwise to some starch, a black substance is formed. The reaction involved is A. dehydration. B. depolymerization. C. redox reaction. D. neutralization. (HKCEE 2002)

35. A part of the flow diagram for the Contact Process is shown below :

Which of the following combinations is correct? X Y Z A. air water concentrated sulphuric acid B. air concentrated sulphric acid oleum C. oxygen sulphur trioxide concentrated sulphuric acid D. oxygen water oleum (HKCEE 2002)

36. When sulphur dioxide is bubbled into water, a colourless solution is formed. Which of the following statements concerning the solution are correct? (1) The solution conducts electricity better than water. (2) The solution can change iron(III) sulphate solution from yellow to green. (3) The solution can change potassium bromide solution from colourless to brown. A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) (HKCEE 2002)

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37. Which of the following set-ups can be used to dry moist sulphur dioxide gas? (1) (2)

(3)

A. B. C. D.

(1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) (HKCEE 2002)

38. Sodium azide, NaN3, is used in air bags in cars. When there is a serious collisions, the azide will decompose to give nitrogen. The decomposition can be represented by the equation : 2NaN3(s) → 2Na(s) + 3N2(g) What is the mass of sodium azide required to produce 72 dm3 of nitrogen at room temperature and pressure? (Relative atomic masses : N =14.0; Na = 23.0; Molar volume of gas at room temperature and pressure = 24.0 dm3) A. 65.0g B. 130.0g C. 195.0g D. 292.5g (HKCEE 2003)

39. Which of the following substances will NOT react with bromine water? A. propene B. sulphur dioxide C. potassium iodide solution - 12 -

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D. ammonium chloride solution (HKCEE 2003) 3

40. A sample of zinc granules of mass 1.8g was added to 100cm of 0.25M hydrochloric acid. What is the theoretical volume of hydrogen produced at room temperature and pressure? (Relative atomic mass : Zn = 65.4; Molar mass of gas at room temperature and pressure = 24.0 dm3) A. 0.30 dm3 B. 0.33 dm3 C. 0.60 dm3 D. 0.66 dm3 (HKCEE 2003)

41. Which of the following solutions would NOT undergo a colour change when mixed with sodium sulphite solution? A. iodine solution B. acidified potassium permanganate solution C. chromium(III) sulphate solution D. iron(III) sulphate solution (HKCEE 2003)

42. X is a bleaching agent. X bleaches a dye by oxidation and becomes Y at the end of the reaction. Which of the following combinations is correct? X Y A. Cl2(aq) Cl-(aq) B. Cl2(aq) OCl-(aq) C. SO2(aq) SO32-(aq) D. SO2(aq) SO42-(aq) (HKCEE 2003)

43. Which of the following statements concerning sulphur is/are correct? (1) It is yellow in colour. (2) It dissolves in water to give an acidic solution. (3) It is used as a raw material in the Contact Process. A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only (HKCEE 2003)

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44. Iron pyrite (FeS2) looks like gold and its common name is “fool’s fold”. Which of the following methods can be used to distinguish iron pyrite from gold? (1) comparing their densities (2) comparing their electrical conductivity (3) comparing the effect of heat on them A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) (HKCEE 2003)

45. A gaseous mixture consists of methane and ethane in a mole ratio of 1:1. It has a volume of 200cm3 at room temperature and pressure. What is the volume of oxygen required, measured at room temperature and pressure, for the complete combustion of the mixture? A. 400 cm3 B. 550 cm3 C. 700 cm3 D. 1100 cm3 (HKCEE 2004)

46. Which of the following substances, when dissolved in water, gives a solution with pH greater than 7? (1) chlorine (2) calcium oxide (3) sulphur dioxide A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only (HKCEE 2004)

47. 1st statement : In the Contact process, oleum instead of water is used to absorb the sulphur trioxide produced. 2nd statement : The reaction of sulphur trioxide with water is highly exothermic. (HKCEE 2004)

48. 1st statement : Sulphur dioxide is used to preserve dried fruits. 2nd statement : Sulphur dioxide is toxic to micro-organisms. (HKCEE 2004) - 14 -

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Directions : Question 49 refers to the following flow scheme for the production of sulphuric acid.

49. Which of the following statements concerning the flow scheme is INCORRECT? A. ZnS is roasted in air in Stage 1. B. Air is used as a reactant in Stage 2. C. Water is used to react with SO3 in Stage 3. D. Heat energy is liberated in Stage 4. (HKCEE 2005)

50. Which of the following combinations correctly describes the difference between sulphur dioxide bleach and chlorine bleach? sulphur dioxide bleach

chlorine bleach

A. bleaching by oxidation

bleaching by reduction

B. faster bleaching action

slower bleaching action

C. temporary bleaching effect D. suitable for bleaching cotton

permanent bleaching effect suitable for bleaching silk (HKCEE 2005)

51. NaHCO3 decomposes upon heating to form Na2CO3, CO2 and H2O. What is the volume of CO2 formed at room temperature and pressure if 336g of NaHCO3 undergoes complete decomposition? A. 12 dm3 B. 24 dm3 C. 48 dm3 D. 96 dm3 (HKCEE 2005)

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Suggested Answers :

1.

B

2.

C

3.

D

4.

D

5.

A

6.

B

7.

B

8.

B

9.

C

10 .

B

11.

D

12 .

A

13 .

D

14 .

C

15 .

D

16 .

B

17 .

A

18 .

B

19 .

B

20 .

C

21 .

C

22 .

D

23 .

B

24 .

D

25 .

B

26 .

C

27 .

C

28 .

B

29 .

C

30 .

D

31 .

A

32 .

B

33 .

C

34 .

A

35 .

B

36 .

A

37 .

B

38 .

B

39 .

D

40 .

A

41 .

C

42 .

A

43 .

C

44 .

D

45 .

B

46 .

B

47 .

C

48 .

A

49 .

C

50 .

C

51 .

C

52 .

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Explanation of M.C. Questions :

1.

statement (1) : correct. The presence of H+ means it has acidic properties, turning blue litmus to red. statement (2) : wrong. statement (3) : correct. It will dehydrate the paper and to form carbon which is responsible for the black color. Ans. : B

2.

1st statement : false. According to Avogadro’s law, all gases under same conditions have same molar volume. nd 2 statement : true. Relative atomic mass of O is 16; while that of H is only 1. Ans. : C

3.

Ans. : D

4.

The chemical equation is : Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g) 224 no. of moles of Fe = 56 = 4 mol no. of moles of Fe 2 = no. of moles of CO 2 3 3 no. of moles of CO2 = 2 × 4 = 6 mol ∴ volume of CO2 = 6 × 24 = 144 dm3 Ans. : D

5.

statement (1) : correct. Examples of sulphide ores are zinc blend and iron pyrite. They burn in air to give SO2. statement (2) : wrong. The equation for the reaction between SO2 and O2 is as follows : 2SO2(g) + O2(g) 2SO3(g) The mole ratio between SO2 and O2 should be 2 : 1. statement (3) : wrong. The absorption of SO3 by water is highly exothermic, thus instead of using water, conc. H2SO4 is used to absorb SO3. Ans. : A

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6.

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experiment A : can’t. conc. H2SO4 behaves as an acid to react with CuO to give CuSO4 and H2O. H2SO4(l) + CuO(s) → CuSO4(s) + H2O(l) experiment B : can. CuSO4•nH2O(s) → CuSO4(s) + nH2O(l) experiment C : can’t. H2SO4 behaves as an acid to react with CaCO3 to give CaSO4, H2O and CO2. H2SO4(l) + CaCO3(s) → CaSO4(s) + CO2(g) + H2O(l) experiment D : can’t. conc. H2SO4 reacts with NaCl(s) to give HCl(g). 2NaCl(s) + H2SO4(l) → Na2SO4(s) + 2HCl(g) Ans. : B

7.

the chemical equation involved : S(s) + O2(g) → SO2(g) 1.6 no. of moles of S = 32.0 = 0.05 mol = no. of moles of SO2 volume of SO2 = 0.05 × 24.0 = 1.2 dm3 Ans. : B

8.

mole ratio = volume ratio the larger the no. of mole, the greater the volume of a gas. substance A : 2CO(g) + O2(g) → 2CO2(g) no. of moles of O2 required = 2 mol substance B : 2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(l) 7 no. of moles of O2 required = 2 = 3.5 mol substance C : C2H4(g) + 3O2(g) → 2CO2(g) + 2H2O(l) no. of moles of O2 required = 3 mol substance D : C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l) no. of moles of O2 required = 3 mol Ans. : B - 18 -

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9.

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the chemical equation involved : vol ( N x O y ) vol ( N 2 )

2NxOy → xN2(g) + yO2(g) =

2 x

=

2 y

60 2 = 60 x x=2 vol ( N x O y ) vol (O2 ) 60 2 = 30 y y=1 Ans. : C 10. statement (1) : wrong. The mass should be 28.0g statement (2) : correct. 4.0 no. of moles of He = 4.0 = 1.0 mol as they are both gases, under same conditions, they have same volume for same no. of moles. statement (3) : wrong. no. of moles of N atoms = 2.0 mol ∴ no. of N atoms = 2.0 × 6.02 × 1023 = 1.204 × 1024 mol Ans. : B 11. reaction (1) : SO2(g) + O2(g) → SO3(g) SO3(g) + H2SO4(l) → H2S2O7(l) H2S2O7(l) + H2O(l) → 2H2SO4(l) The O.N. of S increases from +4 (in SO2) to +6 (in H2SO4). reaction (2) : SO2(g) + H2O(l) + dye → SO42-(aq) + 2H+(aq) + (dye-O) The O.N. increases from +4 in (SO2) to +6 (in SO42-). reaction (3) : SO2(g) + Br2(aq) + 2H2O(l) → SO42-(aq) + 2Br-(aq) + 4H+(aq) The O.N. increases from +4 in (SO2) to +6 (in SO42-). Ans. : D - 19 -

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12. Element X is sulphur. statement (1) : correct. Calcium, a metal reacts with sulphur, a non-metal to give calcium sulphide which is an ionic compound. Ca(s) + S(s) → CaS(s) statement (2) : correct. This oxide is called sulphur dioxide, when dissolved in water, sulphurous acid is formed. SO2(g) + H2O(l) H2SO3(aq) H2SO3(aq) 2H+(aq) + SO32-(aq) statement (3) : wrong. Even in molten state, X doesn’t contain either mobile ions or delocalized electrons. Ans. : A 13. 1st statement : false. The chemical equation involved : Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g) Zn is in excess and HCl is limiting in both experiments. no. of moles of H2 liberated ∝ volume of H2 liberated 1 In the 1st experiment, no. of moles of H2 = 2 × no. of moles of HCl 1 10 = 2 × 10 × 1000 = 0.05 mol 1 50 In the 2nd experiment, no. of moles of H2 = 2 × 2 × 1000 = 0.05 mol In both experiments, no. of moles of H2 liberated are the same, i.e. same volume is obtained. 2nd statement : false. For 2M HCl and 10M HCl, they are both strong acids. Ans. : D

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14. volume of gas ∝ no. of moles of gas 1.0 A : no. of moles of NH3 = 17.0 = 0.0588 mol 2.0 B : no. of moles of N2 = 28.0 = 0.0714 mol 3.0 C : no. of moles of O2 = 32.0 = 0.09375 mol 4.0 D : no. of moles of CO2 = 44.0 = 0.0909 mol Ans. : C 15. Concentrated H2SO4 acts as an oxidizing agent. the chemical equation involved : 2Fe(s) + 6H2SO4(l) → Fe2(SO4)3(aq) + 3SO2(g) + 6H2O(l) (yellow) Ans. : D 16. statement (1) : wrong. Sulphur is not a gas at r.t.p., it is a solid. It doesn’t occupy volume in the air. statement (2) : correct. No. of moles ∝ no. of particles. 2 no. of moles of S = 32.0 = 0.0625 mol 1 no. of moles of O atoms = 32.0 × 2 = 0.0625 mol they have the same no. of atoms. statement (3) : wrong. In 1 mole of O2, there are 2 moles of O atoms. Ans. : B 17. statement (1) : correct. statement (2) : correct. statement (3) : wrong. This statement just tells us H2SO4 is a dibasic acid. Ans. : A

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18. the chemical equation involved : CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g) 7.5 no. of moles of CaCO3 = 100 = 0.075 mol 50.0 no. of moles of HCl = 2× 1000 = 0.1 mol 0.075 mol of CaCO3 require 0.075 × 2 = 0.15 mol of HCl but there is only 0.1 mol of HCl, this HCl is limiting. 1 1 no. of moles of CO2 = 2 × no. of moles of HCl = 2 × 0.1 = 0.05 mol volume of CO2 = 0.05 × 24 = 1.2 dm3 Ans. : B 19. experiment (1) : can. 4FeS2(s) + 11O2(g) → 2Fe2O3(s) + 8SO2(g) experiment (2) : can’t. H2SO4(aq) acts as an acid, reacting with reactive metals to give H2(g). Fe(s) + H2SO4(aq) → FeSO4(aq) + H2(g) experiment (3) : can. H2SO4(l) acts as an oxidizing agent, reacting with metals to give SO2(g). Cu(s) + H2SO4(l) → CuSO4(s) + SO2(g) + 2H2O(l) Ans. : B 20. 1st statement : wrong. Since water is not a gas, so its molar volume is not the same as that of a gas, CO2. nd 2 statement : correct. no. of atoms ∝ no. of moles of atoms no. of moles of atoms in H2O = 3 mol no. of moles of atoms in CO2 = 3 mol Ans. : C

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21. A : wrong. Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g) Zn(s) + 2H2SO4(l) → ZnSO4(aq) + SO2(g) + 2H2O(l) B : wrong. Assume the formula of sugar is C6H12O6. C6H12O6(s) + H2SO4(aq) → no reaction C6H12O6(s) → 6C(s) + 6H2O(l) C : correct. 2NH3(aq) + H2SO4(aq / l) → (NH4)2SO4(aq) D : wrong. Dilute H2SO4(aq) does not have dehydrating property. CuSO4•nH2O(s) + H2SO4(aq) → no reaction CuSO4•nH2O(s) → CuSO4(s) + nH2O(l) Ans. : C 22. The chemical equation involved : I2(aq) + SO2(g) + 2H2O(l) → 2I-(aq) + SO42-(aq) + 4H+(aq) A : wrong. The colour of iodine solution should change from brown to colourless. B : wrong. The final products are aqueous solution. C : wrong. It is a redox reaction. D : correct. The O.N. of S increases from +4 (in SO2) to +6 (in SO42-). Ans. : D 23. The chemical equation involved : Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g) 21.8 no. of moles of Zn = 65.4 = 0.333 mol 250.0 no. of moles of HCl = 2.0 × 1000 = 0.5 mol 0.333 mol of Zn require 0.333 × 2 = 0.666 mol of HCl. There is 0.5 mol of HCl only, it is limiting. 1 1 no. of moles of H2 = 2 × no. of moles of HCl = 2 × 0.5 = 0.25 mol volume of H2 = 0.25 × 24 = 6.0 dm3 Ans. : B

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Textbook (Book 2) : p.267 – 292

24. statement (1) : correct. Cu(s) + 2H2SO4(l) → CuSO4(aq) + SO2(g) + 2H2O(l) statement (2) : correct. Density ∝ molar mass of gas Average molar mass of air = 28.8 g mol-1 Molar mass of SO2 = 64.1 g mol-1 statement (3) : correct. 2NaOH(aq) + SO2(g) → Na2SO3(aq) + H2O(l) Ans. : D 25. 1st statement : true. Assume the formula of filter paper is CnH2mOm. CnH2mOm(s) → nC(s) + mH2O(l) nd 2 statement : true but it doesn’t explain 1st statement. The reason should be conc. H2SO4 behaves as dehydrating agent, dehydrating filter paper black. Ans. : B 26. 1st statement : wrong. Volume occupied by a solid and a gas is different. 2nd statement : correct. They have same no. of moles. Ans. : C 27. the chemical equation involved : 4H2(g) + Fe3O4(s) → 3Fe(s) + 4H2O(l) 96.0 no. of moles of H2 =

1000 = 4.0 mol 24.0

no. of moles of H 2 4 = no. of moles of Fe 3 3 no. of moles of Fe = 4.0 × 4 = 3.0 mol mass of Fe = 3.0 × 55.8 = 168.0 g = 0.168 kg Ans. : C

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PRODUCTS FROM IMORTANT PROCESSES

Textbook (Book 2) : p.267 – 292

600 28. no. of moles of O2 =

1 1000 = 40 24.0

1 1 total no. of atoms = 40 × L × 2 = 20 L Ans. : B 29. statement (1) : correct. It is because ∆H is negative which implies that the reaction is exothermic, heat is released during reaction. statement (2) : wrong. The conditions are not included in the equation. statement (3) : correct. It can be calculated from the stoichiometric constants from the equation. For the reactants, the total no. of moles is 2 mol (1 mol of H2 + 1 mol of Cl2). For the products, the total no. of moles is 2 mol. Ans. : C 30. Ans. : D 31. 1st statement : true. Bromine can react with sodium sulphite but cannot react with sodium sulphate. Br2(aq) + SO32-(aq) + H2O(l) → 2Br-(aq) + SO42-(aq) + 2H+(aq) 2nd statement : true which is the correct explanation for the 1st statement. Bromine is an oxidizing agent and sodium sulphite is a reducing agent. When they react, bromine is reduced to bromide ion; while sulphite is oxidized to sulphate. Ans. : A

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PRODUCTS FROM IMORTANT PROCESSES

Textbook (Book 2) : p.267 – 292

32. the chemical equation involved : X(g) + 3Y(g) → 2Z(g) 40 cm of X should react with 40 × 3 = 120 cm3 of Y. However, there is only 60 cm3 of Y, thus Y is limiting and X is in excess. 3

By Avogadro’s Law, volume of Y 3 = volume of Z 2 2 volume of Z = 60× 3 = 40 cm3 1 After reaction, 40 – 60 × 3 = 20 cm3 of X remains. Volume of the resultant gaseous mixture = volume of X remained + volume of Z produced = 20 + 40 = 60 cm3 Ans. : B 33. no. of molecules ∝ no. of moles 2.0 substance A : 1.0 × 2 = 1.0 mol 16.0 substance B : 16.0 × 2 = 0.5 mol 18.0 substance C : 14.0 + 1.0 × 3 = 1.059 mol 60.0 substance D : 35.5 × 2 = 0.845 mol Ans. : C 34. Assume the formula of starch is CnH2mOm. CnH2mOm

H2SO4(l ) nC(s)

+ mH2O(l)

(black substance)

It is due to dehydrating property of conc. H2SO4. Ans. : A 35. Ans. : B

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PRODUCTS FROM IMORTANT PROCESSES

Textbook (Book 2) : p.267 – 292

36. statement (1) : correct. SO2(g) dissolved in water to give H2SO3(aq) which can ionize in water to give H+ and SO32- ions, which are mobile. Thus the solution is a better electrolyte than water. SO2(g) + H2O(l) H2SO3(aq) H2SO3(aq) 2H+(aq) + SO32-(aq) statement (2) : correct. SO2(aq) is a reducing agent and Fe2(SO4)3 is an oxidizing agent. Redox reaction can occur. The ionic equation is as follows : SO2(aq) + 2Fe3+(aq) + 2H2O(l) → SO42-(aq) + 2Fe2+(aq) + 4H+(aq) statement (3) : wrong. Both SO2(aq) and KBr(aq) are reducing agents. No redox reaction occurs. Ans. : A 37. set-up (1) : can. set-up (2) : can’t. CaO can react with the moist SO2(g). CaO(s) + SO2(g) → CaSO3(s) set-up (3) : can. Ans. : B 38. the chemical equation involved : 2NaN3(s) → 2Na(s) + 3N2(g) 72 no. of moles of N2 = 24 = 3 mol no. of moles of NaN 3 2 = no. of moles of N 2 3 2 no. of moles of NaN3 = 3× 3 = 2 mol mass of NaN3 = 2 × (23.0 + 14.0 × 3) = 130.0 g Ans. : B

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PRODUCTS FROM IMORTANT PROCESSES

Textbook (Book 2) : p.267 – 292

39. Br2(aq) is an oxidizing agent. substance A : can. An addition reaction occurs. 1,2-dibromopropane is formed. CH3CH=CH2

+

Br2

CH3CH-CH2 Br Br

(1,2-dibromopropane) substance B : can. SO2 is a reducing agent. SO2(g) + Br2(aq) + 2H2O(l) → SO42-(aq) + 2Br-(aq) + 4H+(aq) substance C : KI is a reducing agent. Br2(aq) + 2I-(aq) → 2Br-(aq) + I2(aq) substance D : can’t. Br2 can’t react with Cl-(aq). Ans. : D 40. the chemical equation involved : Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g) 1.8 no. of moles of Zn = 65.4 = 0.02752 mol 100 no. of moles of HCl = 0.25 × 1000 = 0.025 mol 0.02752 mol of Zn has to react with 0.02752 × 2 = 0.05504 mol of HCl. There is only 0.025 mol of HCl, it is limiting. no. of moles of HCl 2 = no. of moles of H 2 1 1 no. of moles of H2 = 0.025 × 2 = 0.0125 mol By Avogadro’s Law, volume of H2 produced = 0.0125 × 24.0 = 0.30 dm3 Ans. : A

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PRODUCTS FROM IMORTANT PROCESSES

Textbook (Book 2) : p.267 – 292

41. Na2SO3(aq) is a reducing agent. It can only reacts with oxidizing agents. substance A : can. I2 is an oxidizing agent. I2(aq) + SO32-(aq) + H2O(l) → 2I-(aq) + SO42-(aq) + 2H+(aq) substance B : can. KMnO4 / H+ is an oxidizing agent. 2MnO4-(aq) + 5SO32-(aq) + 6H+(aq) → 2Mn2+(aq) + 5SO42-(aq) + 3H2O(l) substance C : can’t. substance D : can. Fe2(SO4)3 is an oxidizing agent. SO32-(aq) + 2Fe3+(aq) + H2O(l) → SO42-(aq) + 2Fe2+(aq) + 2H+(aq) Ans. : C 42. Between Cl2(aq) and SO2(aq), Cl2(aq) bleaches substances through oxidation. The following chemical equations involved : Cl2(aq) + H2O(l) → HCl(aq) + HOCl(aq) HOCl(aq) H+(aq) + OCl-(aq) OCl-(aq) + dye → Cl-(aq) + (dye + O) Ans. : A 43. sentence (1) : correct. Sulphur is a yellow solid under room temperature and pressure. sentence (2) : wrong. Sulphur is insoluble in water. sentence (3) : correct. Sulphur is oxidized to SO2, which is in turn further oxidized to SO3. It dissolved in conc. H2SO4 to give oleum, H2S2O7. Finally, oleum dissolved in water to give conc. H2SO4. Ans. : C 44. Ans. : C

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PRODUCTS FROM IMORTANT PROCESSES

Textbook (Book 2) : p.267 – 292

45. the chemical equations involved : CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) 2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(l) since the mole ratio of CH4 and C2H6 is 1 : 1, thus the volume ratio is also 1 : 1, i.e. volume of CH4 = 100 cm3 and volume of C2H6 = 100 cm3 Volume of CH 4 1 = Volume of O 2 2 Volume of O2 = 200 cm3 Volume of C 2 H 6 2 = Volume of O 2 7 Volume of O2 = 350 cm3 Total volume of O2 required = 350 + 200 = 550 cm3 Ans. : B 46. pH value > 7 means the solution is alkaline. substance (1) : wrong. Cl2(g) dissolved in water to give an acidic solution. Cl2(g) + H2O(l) HCl(aq) + HOCl(aq) HCl(aq) → H+(aq) + Cl-(aq) substance (2) : correct. CaO(s) dissolved in water to give calcium hydroxide solution, which is alkaline. CaO(s) + H2O(l) → Ca(OH)2(aq) substance (3) : wrong. SO2(g) dissolved in water to give an acidic solution. SO2(g) + H2O(l) H2SO3(aq) H2SO3(aq) 2H+(aq) + SO32-(aq) Ans. : B 47. 1st statement : false. Concentrated H2SO4 is used instead of oleum to absorb SO3(g). 2nd statement : true. Ans. : C 48. 1st statement : true. SO2(g) is a food preservative and an anti-oxidant. 2nd statement : true. It is the correct explanation of the 1st statement. Ans. : A - 30 -

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49. A : correct. 2ZnS(s) + 2O2(g, from the air) → 2ZnO(s) + SO2(g) B : correct. 2SO2(g) + O2(g) 2SO3(g) conditions : 450℃, 1 atm and V2O5 as a catalyst C : wrong. Concentrated H2SO4 is used instead of water to react with SO3(g). SO3(g) + H2SO4(l) → H2S2O7(l) D : correct. This process is exothermic, heat is liberated. Ans. : C 50. Ans. : C 51. the chemical equation involved : heating

2NaHCO3(s)

Na2CO3(s) + CO2(g) + H2O(l)

336 no. of moles of NaHCO3 = 23 + 1 + 12 + 16 × 3 = 4 4 no. of moles of CO2 formed = 2 = 2 volume of CO2 produced = 2.0 × 24.0 = 48.0 dm3 Ans. : C

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