nss chemistry part 7 redox reactions chemical cells and electrolysis _mc

NSS Chemistry Part VII Redox Reactions, Chemical Cells and Electrolysis(HKCE Past Paper Questions)

1. 1995 Q10 In which of the following equations does the underlined substance become reduced?A. CuSO4 + Zn ZnSO4 + Cu B. 2FeCl2 + Cl2 2FeCl3 C. Pb(OH)2 + 2HNO3 Pb(NO3)D. MgCO3 + 2HCl MgCl2 + CO

2. 1995 Q11 A student tries to electroplate an iron ring with nickel using the set

Which of the following combinations is correct? Solution X A. Iron(II) sulphate solution B. Iron(II) sulphate solution C. Nickel(II) sulphate solution D. Nickel(II) sulphate solution

3. 1995 Q17 Compound X is a white solid. When X is warmed with sodium hydroxide solution, a gas is evolved which turns

moist red litmus paper blue. When chlorine water is added to an aqueous solution of X, a brown solution is formed. X is probably

A. ammonium bromide. B. ammonium chloride. C. sodium bromide. D. sodium chloride.

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Redox Reactions, Chemical Cells and Electrolysis(HKCE Past Paper Questions) Multiple Choice Questions

In which of the following equations does the underlined substance become reduced?

)2 + 2H2O + CO2 + H2O

A student tries to electroplate an iron ring with nickel using the set-up shown below.

Which of the following combinations is correct? Anode Cathode Iron ring Nickel rod Nickel rod Iron ring

Nickel(II) sulphate solution Iron ring Nickel rod Nickel(II) sulphate solution Nickel rod Iron ring

Compound X is a white solid. When X is warmed with sodium hydroxide solution, a gas is evolved which turns moist red litmus paper blue. When chlorine water is added to an aqueous solution of X, a brown solution is

Redox Reactions, Chemical Cells and Electrolysis

In which of the following equations does the underlined substance become reduced?

Ans: A

up shown below.

Ans: D

Compound X is a white solid. When X is warmed with sodium hydroxide solution, a gas is evolved which turns moist red litmus paper blue. When chlorine water is added to an aqueous solution of X, a brown solution is

Ans: A

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4. 1995 Q30-31 Directions : Questions 4 and 5 refer to the following chemical equation : Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2(g)

Which of the following statement is/are correct? (1) Carbon monoxide is an oxidizing agent. (2) The oxidation number of carbon changes from +2 to +4. (3) The oxidation number of iron changes from +2 to 0.

A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only

Ans: B

5. 1995 Q31 What volume of carbon dioxide, measured at room temperature and pressure, is produced if 224 g 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

Ans: D

6. 1995 Q33 Which of the following statements concerning a silver oxide cell is/are correct? (1) The cell is rechargeable. (2) The cell can maintain a steady voltage during discharge. (3) The positive electrode of the cell is silver oxide.


Ans: D

7. 1995 Q37 In the set-up shown below metal X is more reactive than metal Y.

Which of the following statements concerning this set(1) Electrolysis occurs inside the lemon.(2) Chemical energy is changed into electrical energy.(3) Electrons flow from metal Y to metal X in the external circuit.


8. 1995 Q40 Which of the following methods can produce hydrogen?(1) adding zinc to water (2) electrolyzing dilute sulphuric acid(3) adding magnesium to dilute hydrochloric acid

A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3)

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up shown below metal X is more reactive than metal Y.

Which of the following statements concerning this set-up is/are correct? Electrolysis occurs inside the lemon. Chemical energy is changed into electrical energy.

om metal Y to metal X in the external circuit.

Which of the following methods can produce hydrogen?

electrolyzing dilute sulphuric acid hydrochloric acid

Ans: B

Ans: C

9. 1996 Q7

Which of the following metals would produce the smallest voltage in the above setA. iron B. aluminium C. copper D. magnesium

10. 1996 Q25

step 1 step 2N2 NH3Which of the above flow chart involved the largest change in oxidation number of nitrogen?A. step 1 B. step 2 C. step 3 D. step 4

11. 1996 Q27

Which of the following statements concerning the above setA. Electrons flow from the lead electrode to the magnesium electrode through the external circuit.B. Electrons flow through the salt bridge.C. The mass of the lead electrode remains unchanged.D. Oxidation occurs at the magnesium electrode.

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Which of the following metals would produce the smallest voltage in the above set-up?

step 2 step 3 step 4NO NO2 HNO3

Which of the above flow chart involved the largest change in oxidation number of nitrogen?

Which of the following statements concerning the above set-up is correct? lead electrode to the magnesium electrode through the external circuit.

Electrons flow through the salt bridge. The mass of the lead electrode remains unchanged. Oxidation occurs at the magnesium electrode.

up?

Ans: C

Which of the above flow chart involved the largest change in oxidation number of nitrogen?

Ans: B

lead electrode to the magnesium electrode through the external circuit.

Ans: D

12. 1996 Q30-31 Directions : Q.12 and Q.13 refer to the following experiment.

Which of the following combinations is correct? Gas X Gas Y A. chlorine hydrogen B. chlorine oxygen C. hydrogen chlorine D. oxygen hydrogen

13. 1996 Which of the following statements concerning t(1) Platinum electrodes should be used.(2) The concentration of Na+(aq) ions around the cathode increases.(3) The solution changes from colourless to pink.


14. 1996 Q35 In which of the following processes will lead be produced?(1) the electrolysis of molten lead(II) bromide(2) heating lead(II) oxide strongly (3) adding magnesium to lead(II) nitrate solution


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refer to the following experiment.

Which of the following combinations is correct?

Which of the following statements concerning the above experiment is/are correct? Platinum electrodes should be used.

ions around the cathode increases. The solution changes from colourless to pink.

In which of the following processes will lead be produced? the electrolysis of molten lead(II) bromide

adding magnesium to lead(II) nitrate solution

Ans: A

Ans: D

Ans: C

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15. 1996 Q37 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 decolorization of bromine water


Ans: D

16. 1996 Q38 Which of the following substances are commonly found in the waste water produced by electroplating

factories? (1) acids (2) alkalis (3) cyanides


Ans: D 17. 1997 Q7 During the electrolysis of 1 M copper(II) chloride solution using copper electrodes, which of the following

changes would occur at the electrodes? Cathode Anode A. hydrogen liberated chlorine liberated B. copper deposited chlorine liberated C. copper dissolved copper deposited D. copper deposited copper dissolved

Ans: D

18. 1997 Q8 Which of the following conversions involves the smallest change in oxidation number of the underlined

element? A. C(s) CO2(g) B. NO3(aq) NO2(g) C. SO32(aq) SO42(aq) D. MnO4(aq) Mn2+(aq)

Ans: B

19. 1997 Q11

A zinc-carbon cell is connected to a voltmeter as shown in the above diagram. Which of the following statements concerning the set-up is

A. Electrons flow from the zinc case to the carbon rod in the external circuit.B. The zinc case gradually becomes thinner as the cell discharges.C. Manganese(IV) oxide acts as an oxidizing agent.D. Ammonium chloride acts as a reducing agent.

20. 1997 Q21 The following equation represents the reaction of chlorine with dilute sodium hydroxide solution at room

temperature : Cl2(g) + 2NaOH(aq) NaCl(aq) + NaClO Which of the following statements concerning this reaction is correct?

A. Chlorine is oxidized and sodium hydroxide is reduced.B. Chlorine is reduced and sodium hydroxide is oxidized.C. Chlorine is simultaneously oxidized and reduced.D. Sodium hydroxide is simultaneously oxidized and reduced.

21. 1997 Q29 An iron nail is heated with concentrated sulphu

Gas given off Colour of solution formed A. hydrogen pale green B. hydrogen yellow C. sulphur dioxide pale green D. sulphur dioxide yellow

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carbon cell is connected to a voltmeter as shown in the above diagram. Which of the following up is INCORRECT?

inc case to the carbon rod in the external circuit. The zinc case gradually becomes thinner as the cell discharges. Manganese(IV) oxide acts as an oxidizing agent. Ammonium chloride acts as a reducing agent.

ation represents the reaction of chlorine with dilute sodium hydroxide solution at room

+ NaClO(aq) + H2O(l) Which of the following statements concerning this reaction is correct?

dium hydroxide is reduced. Chlorine is reduced and sodium hydroxide is oxidized. Chlorine is simultaneously oxidized and reduced. Sodium hydroxide is simultaneously oxidized and reduced.

An iron nail is heated with concentrated sulphuric acid. Which of the following combinations is correct?

Colour of solution formed pale green

pale green

carbon cell is connected to a voltmeter as shown in the above diagram. Which of the following

Ans: D

ation represents the reaction of chlorine with dilute sodium hydroxide solution at room

Ans: C

ric acid. Which of the following combinations is correct?

Ans: D

22. 1997 Q36 Which of the following substances can be used to distinguish between concentrated nitric acid and concentrated

sulphuric acid? (1) sodium carbonate powder (2) copper turnings (3) cane sugar


23. 1998 Q4-5 Directions : Questions 23 and 24 refer to the following experiment:The circuit shown below is set up and the

solid lead(II) bromide is heated until it becomes molten.

Which of the following statements concerning the experiment is A. The bulb lights up. B. A reddish brown gas is liberated at electrodeC. Electrodes X and Y can be made of nichrome.D. Oxidation occurs at electrode Y

24. 1998 Q5 Which of the following can be deduced from the experimental result?A. Solid lead(II) bromide contains mobileB. Molten lead(II) bromide contains delocalized electrons.C. Molten lead(II) bromide can be decomposed by electricity.D. Solid lead(II) bromide is a covalent compound but molten lead(II) bromide is an ionic compound.

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ing substances can be used to distinguish between concentrated nitric acid and concentrated

refer to the following experiment:The circuit shown below is set up and the solid lead(II) bromide is heated until it becomes molten.

Which of the following statements concerning the experiment is INCORRECT?

A reddish brown gas is liberated at electrode X. can be made of nichrome.

Y.

Which of the following can be deduced from the experimental result? Solid lead(II) bromide contains mobile ions. Molten lead(II) bromide contains delocalized electrons. Molten lead(II) bromide can be decomposed by electricity. Solid lead(II) bromide is a covalent compound but molten lead(II) bromide is an ionic compound.

ing substances can be used to distinguish between concentrated nitric acid and concentrated

Ans: C

refer to the following experiment:The circuit shown below is set up and the

Ans: B

Solid lead(II) bromide is a covalent compound but molten lead(II) bromide is an ionic compound. Ans: C

25. 1998 Q12

A gas X is bubbled into a solution of would X react with Y?

X Y A. ammonia potassium iodide B. chlorine potassium nitrate C. carbon dioxide sodium hydroxide D. sulphur dioxide iron(II) sulphate

26. 1998 Q20 The following equation represents the reaction of an oxide of lead with hydrogen: Pb3O4(s) + 4H2(g) 3Pb(s) + 4H What mass of lead would be obtained if 68.5 g of the oxide was consumed in the reaction? (Relative atomic mass : O = 16.0, Pb = 207.0)

A. 20.7 g B. 41.4 g C. 62.1 g D. 82.8 g

27. 1998 Q21 Consider the following experiment.

Which of the following statements concerning the above experiment is correct?A. Permanganate ions migrate into the salt bridge.B. Electrons flow from electrode XC. Carbon electrodes are used because they are chemically inert.D. The half equation for the change occurring at electrode

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bubbled into a solution of Y as shown in the above diagram. In which of the following combinations

Y potassium iodide potassium nitrate sodium hydroxide ron(II) sulphate

The following equation represents the reaction of an oxide of lead with hydrogen: + 4H2O(l)

What mass of lead would be obtained if 68.5 g of the oxide was consumed in the reaction?tive atomic mass : O = 16.0, Pb = 207.0)

Consider the following experiment.

Which of the following statements concerning the above experiment is correct? Permanganate ions migrate into the salt bridge.

X to electrode Y in the external circuit. Carbon electrodes are used because they are chemically inert. The half equation for the change occurring at electrode Y is Fe2+ + 2e Fe.

as shown in the above diagram. In which of the following combinations

Ans: C

What mass of lead would be obtained if 68.5 g of the oxide was consumed in the reaction?

Ans: C

Ans: C

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28. 1998 Q22 In which of the following reactions does the underlined substance act as a reducing agent?

A. SO2 + 2H2S 3S + 2H2O B. Pb(NO3)2 + H2SO4 PbSO4 + 2HNO3 C. 2HCl + MgO MgCl2 + H2O D. 2KBr + Cl2 2KCl + Br2

Ans: D

29. 1998 Q27 Consider the following chemical equation : Zn + pMnO2 + qNH4+ Zn2+ + xMn2O3 + yNH3 + zH2O Which of the following combinations is correct?

x y z

A. 1 2 1 B. 1 3 2 C. 2 3 2 D. 2 2 3

Ans: A

30. 1999 Q8 Iron can be produced from iron(III) oxide by the following reaction: Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2(g) What mass of iron(III) oxide is required to produce 2.1 g of iron? (Relative atomic masses: O = 16.0, Fe = 56.0)

A. 3.0 g B. 4.5 g C. 6.0 g D. 9.0 g

Ans: A

31. 1999 Q9 In which of the following reactions is the underlined reactant reduced?

A. Cu2+ + 2OH Cu(OH)2 B. SO2 + 2Mg 2MgO + S C. 2NH3 + 3CuO 3Cu + N2 + 3H2O D. Zn + 2AgNO3 Zn(NO3)2 + 2Ag

Ans: B

32. 1999 Q10 Which of the following statements concerning bromine and chlorine is

A. They exist as diatomic molecules.B. Their atoms have the same number of oC. They formed ions with a single negative charge.D. Bromine is a stronger oxidizing agent than chlorine.

33. 1999 Q12 Consider the electrolysis experiment shown below:

Which of the following statement concerning this exp

A. The mass of the impure copper rod decreases.B. The blue colour of the copper(II) sulphate solution gradually fades off.C. Oxidation takes place at the pure copper rod.D. The electrolysis process can enhance the corrosion resistan

34. 1999 Q15 Potassium permanganate solution acidified with dilute sulphuric acid is a commonly

Dilute nitric acid is not used to acidify potassium permanganate solution becauseA. nitric acid is more expensive thaB. dilute nitric acid is an oxidizing agent and would react with the reducing agent.C. nitric acid decomposes more readily than sulphuric acid.D. dilute nitric acid would react with potassium permanganate solution.

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Which of the following statements concerning bromine and chlorine is INCORRECTThey exist as diatomic molecules. Their atoms have the same number of outermost shell electrons. They formed ions with a single negative charge. Bromine is a stronger oxidizing agent than chlorine.

Consider the electrolysis experiment shown below:

Which of the following statement concerning this experiment is correct?

The mass of the impure copper rod decreases. The blue colour of the copper(II) sulphate solution gradually fades off. Oxidation takes place at the pure copper rod. The electrolysis process can enhance the corrosion resistance of copper.

Potassium permanganate solution acidified with dilute sulphuric acid is a commonlyDilute nitric acid is not used to acidify potassium permanganate solution because

nitric acid is more expensive than sulphuric acid. dilute nitric acid is an oxidizing agent and would react with the reducing agent. nitric acid decomposes more readily than sulphuric acid. dilute nitric acid would react with potassium permanganate solution.

INCORRECT?

Ans: D

Ans: A

Potassium permanganate solution acidified with dilute sulphuric acid is a commonly-used oxidizing agent.

Ans: B

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35. 1999 Q21 Consider the following chemical equation: 2HNO3 + xFeSO4 + yH2SO4 zFe2(SO4)3 + 4H2O + 2NO Which of the following combinations is correct?

x y z

A. 2 1 1 B. 4 3 2 C. 6 2 3 D. 6 3 3

Ans: D 36. 1999 Q31

Which of the following metal oxides CANNOT be reduced by heating with carbon? (1) magnesium oxide (2) lead(II) oxide (3) iron(III) oxide


Ans: A

37. 1999 Q32 Which of the following substances can react with acidified potassium permanganate solution? (1) ethene (2) copper(II) sulphate solution (3) iron(II) sulphate solution


Ans: C

38. 1999 Q33 Which of the following reactions will occur when aluminium powder is added to silver

(1) displacement (2) anodization (3) redox


39. 1999 Q36 The equation below represents the reaction of chlorine with hot concentrated potassium hydroxide soluti 3Cl2(g) + 6KOH(aq) 5KCl(aq) + KClO Which of the following statements concerning this reaction is/are correct?

(1) Potassium hydroxide acts as a reducing agent.(2) The oxidation number of chlorine changes from 0 to (3) The oxidation number of chlorine changes from 0 to +5.


40. 1999 Q40 Consider the following chemical cell:

Which of the following changes would lead to an increase in the voltage of the (1) The zinc electrode is replaced with a magnesium electrode.(2) The copper electrode is replaced with an iron electrode.(3) The sodium chloride solution is replaced with a sugar solution.


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Which of the following reactions will occur when aluminium powder is added to silver

The equation below represents the reaction of chlorine with hot concentrated potassium hydroxide soluti+ KClO3(aq) + 3H2O(l)

Which of the following statements concerning this reaction is/are correct? Potassium hydroxide acts as a reducing agent. The oxidation number of chlorine changes from 0 to 1.

tion number of chlorine changes from 0 to +5.

Consider the following chemical cell:

Which of the following changes would lead to an increase in the voltage of the cell?The zinc electrode is replaced with a magnesium electrode. The copper electrode is replaced with an iron electrode. The sodium chloride solution is replaced with a sugar solution.

Which of the following reactions will occur when aluminium powder is added to silver nitrate solution?

Ans: C

The equation below represents the reaction of chlorine with hot concentrated potassium hydroxide solution:

Ans: D

cell?

Ans: A

41. 1999 Q42 Consider the following experiment:

Which of the following statements concerning the experiment are correct?(1) Gas bubbles are evolved at electrode (2) An orange colour gradually appears in the solution around electrod(3) The experiment can be used to show that ions migrate towards oppositely charged electrodes.


42. 2000 Q5 Which of the following gases are the major products l

chloride solution using carbon electrodes? Cathode Anode A. hydrogen chlorine B. chlorine hydrogen C. hydrogen oxygen D. oxygen hydrogen

43. 2000 Q6 Which of the following pairs of co

dichromate solution? A. ethane and ethene B. ethanol and propan-1-ol C. sodium carbonate and sodium hydrogencarbonateD. sodium sulphite and sodium sulphate

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Consider the following experiment:

Which of the following statements concerning the experiment are correct? Gas bubbles are evolved at electrode X. An orange colour gradually appears in the solution around electrode Y. The experiment can be used to show that ions migrate towards oppositely charged electrodes.

Which of the following gases are the major products liberated in the electrolysis of concentrated sodium chloride solution using carbon electrodes?

Which of the following pairs of compounds can be distinguished by treating with an acidified potassium

sodium carbonate and sodium hydrogencarbonate sodium sulphite and sodium sulphate

The experiment can be used to show that ions migrate towards oppositely charged electrodes.

Ans: D

iberated in the electrolysis of concentrated sodium

Ans: A

mpounds can be distinguished by treating with an acidified potassium

Ans: D

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44. 2000 Q14 Which of the following solutions can react with bromine water to give a colourless solution? A. sodium chloride solution B. sodium sulphite solution C. sodium iodide solution D. sodium hypochlorite solution

Ans: B

45. 2000Q16 Consider the following equation: 3Zn(s) + 2NO3(aq) + 8H+(aq) 3Zn2+(x) + 2NO(y) + 4H2O(z) Which of the following combinations is correct?

x y z

A. aq g aq B. aq g l C. aq aq l D. l g aq

Ans: B

46. 2000 Q28 Which of the following changes is NOT a redox reaction? A. Fe2(SO4)3 + H2S 2FeSO4 + S + H2SO4 B. 2Al + 6HCl 2AlCl3 + 3H2 C. CaCO3 + CO2 + H2O Ca(HCO3)2 D. 2KClO3 2KCl + 3O2

Ans: C

47. 2000 Q30 In which of the following substances does nitrogen has the smallest oxidation number? A. NH3 B. NO C. N2O D. N2

Ans: A

48. 2000 Q35 Consider the chemical cell shown below:

Which of the following statements concerning the cell is/are correct?(1) Oxidation takes place at the copper electrode.(2) The concentration of magnesium ions in beaker (3) The salt bridge allows electrons to flow from one electrode to the other ele


49. 2000 Q43 Which of the following statements concerning a zinc(1) The ammonium chloride in the cell acts as an electrolyte.(2) The manganese(IV) oxide in the cell act(3) The zinc case of the cell acts as the positive terminal.


50. 2001 Q19 Consider the half equations of a redox reaction: 8H+(aq) + MnO4(aq) + 5e Mn C2O42(aq) 2CO2(g) + 2e

How many moles of MnO4(aq) ions will react completely with one mole of CA. 0.4 B. 1.0 C. 2.5 D. 5.0

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Consider the chemical cell shown below:

Which of the following statements concerning the cell is/are correct? Oxidation takes place at the copper electrode. The concentration of magnesium ions in beaker X increases. The salt bridge allows electrons to flow from one electrode to the other electrode.

Which of the following statements concerning a zinc-carbon cell are correct? The ammonium chloride in the cell acts as an electrolyte. The manganese(IV) oxide in the cell acts as an oxidizing agent. The zinc case of the cell acts as the positive terminal.

Consider the half equations of a redox reaction: Mn2+(aq) + 4H2O(l) + 2e

ions will react completely with one mole of C2O42(aq)

ctrode.

Ans: B

Ans: A

(aq) ions?

Ans: A

51. 2001 Q22 Which of the following equations represent a redox reaction?

A. NH4+(aq) + OH(aq) NH3(g) + HB. 2CrO42(aq) + 2H+(aq) Cr2O72(aq)C. 2FeSO4(s) Fe2O3(s) + SO3(g) + SOD. 2NaHCO3(s) Na2CO3(s) + H2O

52. 2001 Q24 Consider the half equation: IO3(aq) + xH2O(l) + ye I(aq) + zOH Which of the following combinations is correct?

x y A. 1 2 B. 2 4 C. 3 6 D. 4 8

53. 2001 Q29 The oxidation number of lead in [Pb(OH)A. 2. B. +2. C. +4 D. +6

54. 2001 Q44 Consider the set-up shown below:

Which of the following statements are correct?(1) The solution around electrode X(2) The mass of electrode X remains unchanged.(3) Reduction occurs at electrode Y


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Which of the following equations represent a redox reaction? + H2O(l)

(aq) + H2O(l) + SO2(g) O(l) + CO2(g)

+ zOH(aq) of the following combinations is correct?

z

2 4 6 8

The oxidation number of lead in [Pb(OH)4]2 is

atements are correct? X turns brown.

remains unchanged. Y.

Ans: C

Ans: C

Ans: B

Ans: D

55. 2002 Q6 Compound X dissolves in water to give a colourless solution. When chlorine gas is bubbles into the solution,

the solution turns brown. X is probablyA. ammonium iodide. B. iron(II) sulphate. C. sodium sulphite D. potassium hydroxide.

56. 2002 Q7 Sodium chromate, Na2CrO4, dissolves

added to the solution, the following reaction occurs : 2CrO42(aq) + 2H+(aq) Cr2O72(aq) + H

Which of the following statements concerning this reaction is correct?A. The colour of the solution changes from yellow to green.B. Chromate ions act as a reducing agent.C. The oxidation number of oxygen remains unchanged during the reaction.D. The reaction is a neutralization.

57. 2002Q10 Consider the set-up shown below :

Electrons flow from X to Y in the external circuit. Which of the following combinations is correct? X Y

A. carbon silver B. zinc magnesiumC. carbon carbon D. zinc carbon

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n water to give a colourless solution. When chlorine gas is bubbles into the solution, is probably

, dissolves in water to give a yellow solution. When dilute hydrochloric acid is added to the solution, the following reaction occurs :

+ H2O(l) Which of the following statements concerning this reaction is correct?

the solution changes from yellow to green. Chromate ions act as a reducing agent. The oxidation number of oxygen remains unchanged during the reaction. The reaction is a neutralization.

in the external circuit. Which of the following combinations is correct?Z

silver nitrate solution magnesium magnesium sulphate solution

copper(II) sulphate solution silver nitrate solution

n water to give a colourless solution. When chlorine gas is bubbles into the solution,

Ans: A

in water to give a yellow solution. When dilute hydrochloric acid is

Ans: C

in the external circuit. Which of the following combinations is correct?

Ans: D

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58. 2002Q13 Which of the following equations represents a redox reaction? A. Ca(HCO3)2 + 2HCl CaCl2 + 2CO2 + 2H2O B. PCl3 + Cl2 PCl5 C. Fe3+ + 3OH Fe(OH)3 D. Al2O3 + 2NaOH 2NaAlO2 + H2O

Ans: B 59. 2002 Q14 Ammonium dichromate, (NH4)2Cr2O7, decomposes on heating to give chromium(III) oxide, water and nitrogen.

What mass of water is obtained when 126 g of ammonium dichromate undergoes complete decomposition? (Relative atomic masses : H = 1.0, N = 14.0, O = 16.0, Cr = 52.0)

A. 9 g B. 18 g C. 36 g D. 72 g

Ans: C 60. 2002 Q18

The symbol of vanadium is V. What is the oxidation number of vanadium in NH4VO3? A. 1 B. +3 C. +5 D. +6

Ans: C 61. 2002 Q19

Which of the following acids, when heated with copper, would produce a gas? A. dilute nitric acid B. dilute hydrochloric acid C. dilute sulphuric acid D. concentrated ethanoic acid

Ans: A 62. 2002 Q39

Which of the following statements concerning Group VII elements and their ions are correct? (1) Chlorine has the highest oxidizing power among chlorine, bromine and iodine. (2) Iodide ions have the highest reducing power among chloride, bromide and iodide ions. (3) Bromine is a volatile liquid at room temperature and pressure.


Ans: D

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63. 2002 Q41 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)

Ans: A 64. 2003 Q5

Which of the following methods can be used to obtain aluminium from aluminium oxide? A. reducing the oxide with carbon B. heating the oxide strongly. C. electrolysis of the molten oxide D. heating the oxide with iron powder.

Ans: C 65. 2003 Q13

Which of the following substances will NOT react with bromine water? A. propene B. sulphur dioxide C. potassium iodide solution D. ammonium chloride solution

Ans: D 66. 2003 Q15 In the electrolysis of a copper(II) sulphate solution, copper is used as the anode and carbon as the cathode.

Which of the following statements concerning this electrolysis is correct? A. The concentration of Cu2+(aq) ions in the solution remains unchanged. B. The concentration of H+(aq) ions in the solution increases. C. O2(g) is liberated at the anode. D. H2(g) is liberated at the cathode.

Ans: A 67. 2003 Q16

Which of the following conversions is NOT a reduction? A. Fe2O3 Fe B. Cu(OH)2 CuO C. CH3CO2H CH3CH2OH D. H2SO4 SO2

Ans: B

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68. 2003 Q21 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

Ans: C

69. 2003 Q23 Consider the following equation:

5H2S(g) + 2KMnO4(aq) + 3H2SO4(aq) 5S(x) + 8H2O(y) + 2MnSO4(z) + K2SO4(aq)

Which of the following combinations is correct? x y z

A. s aq aq B. s l aq C. aq aq s D. aq l s

Ans: B

70. 2003 Q24 What is oxidation number of sulphur in H2S2O7? A. +2 B. +4 C. +6 D. +8

Ans: C

71. 2003 Q35 Which of the following is/are advantage(s) of using alkaline manganese cells over zinc-carbon cells in cassette players? (1) Alkaline manganese cells have longer life time. (2) Alkaline manganese cells are rechargeable. (3) Alkaline manganese cells give a more steady voltage over discharge.


Ans: C

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72. 2004 Q18 Which of the following reagents can be used to distinguish sodium bromide solution from sodium chloride

solution? A. bromine water B. chlorine water C 1,1,1-trichloroethane D. potassium fluoride solution

Ans: B

73. 2004 Q24 Which of the following combinations concerning the set-up shown below is correct after a current has flowed

through the external circuit for some time?

Mass of anode Colour intensity of the Copper(II) sulphate solution

A. increases no change B. decreases no change C. increases decreases D. decreases decreases

Ans: B

74. 2004 Q32 Which of the following substances can decolourise acidified potassium permanganate solution? (1) sodium nitrate solution (2) sodium sulphite solution (3) chlorine water A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only

Ans: B

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75. 2004 Q39 Which of the following gases can act as reducing agents? (1) ammonia (2) hydrogen (3) fluorine A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3)

Ans: A

76. 2004 Q40 Consider the chemical cell shown below:

Which of the following statements concerning the cell are correct? (1) Electrons flow from electrode X to electrode Y in the external circuit. (2) Oxidation occurs at electrode Y. (3) A blue colour appears in the KI(aq) after the cell has operated for some time.


Ans: B

77. 2005 Q8 Which of the following is NOT a redox reaction?

A. NH4NO3 N2O + H2O B. NH3 + HNO3 NH4NO3

C. N2O4 + H2O HNO2 + HNO3 D. 4HNO3 2H2O + 4NO2 + O2

Ans: B

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78. 2005 Q31 In which of the following combinations will oxygen be produced as the major product at the anode during electrolysis?

electrolyte cathode anode A. 0.1 M CuCl2 platinum platinum B. 0.1 M CuCl2 copper copper C. 5 M HCl platinum platinum D. 5 M HCl copper copper

Ans: A 79. 2006 Q3

What is the oxidation number of cobalt in Co(NH3)4Cl2?

A. 2 B. 0 C. +2 D. +6

Ans: C

80. 2006 Q8 Consider the following chemical equation:

xVO2+ (aq) + yH+(aq) + 2I (aq) xVO2+(aq) + zH2O(l) + I2(aq)

(V is the symbol for the element vanadium.)

Which of the following combinations is correct?

x

y z

A. 1 2 1 B. 1 4 2 C. 2 4 2 D. 3 6 3

Ans: C

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81. 2006 Q21 When substance X is treated with aqueous solution of iron(II) sulphate, the iron(II) ions act as oxidising agent. X may be

A. concentrated hydrochloric acid. B. aqueous ammonia. C. acidified potassium dichromate solution. D. zinc granules.

Ans: D

82. 2006 Q27 Which of the following reaction involve oxidation and reduction?

(1) 2KClO3(s) 2KCl(s) + 3O2(g) (2) Pb(s) + PbO2(s) + 2H2SO4(aq) 2PbSO4(s) + 2H2O(l) (3) H2O2(aq) + H2SO4(aq) +3KI(aq) K2SO4(aq) + I2(aq) + 2H2O(l)

A. (1) and (2) only B . (1) and (3) only C. (2) and (3) only D. (1), (2) and (3)

Ans: D

83. 2006 Q32 Which of the following combinations is correct for a zinc-carbon cell?

Anode

Cathode Electrolyte

A. zinc graphite manganese(IV) oxide B. zinc graphite ammonium chloride C. graphite zinc manganese(IV) oxide D. graphite zinc ammonium chloride

Ans: B

26

84. 2006 Q33 In an experiment, a copper plate and a zinc plate are placed in a beaker containing dilute sulphuric acid. The two metal plates are touching each other as shown in the diagram below:

Which of the following statements correctly describes the observation in the experiment? A. The solution in the beaker turns blue. B. The mass of the zinc plate remains unchanged. C. A white precipitate is formed in the beaker. D. Gas bubbles are formed on the surface of the copper plate.

Ans: D 85. 2006 Q34

Which of the following changes occurs after an aluminium article has been anodised?

A. Its electrical conductivity increases. B. Its tensile strength increases. C. It becomes more easily dyed. D. It becomes more easily oxidised.

Ans: C

86. 2006 Q38 Consider the conversions between three nitrogen compounds shown in the flow diagram below:

Which of the following statements is correct?

A. Reaction 1 occurs spontaneously when nitrogen monoxide is exposed to air. B. The oxidation number of nitrogen remains unchanged in Reaction 2. C. Reaction 3 can be brought about by adding very dilute nitric acid to magnesium. D. Reaction 4 can be brought about by adding concentrated nitric acid to copper.

Ans: A

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87. 2006 Q40 The set-up below shows a chemical cell connected to a voltmeter:

In the set-up, electrons flow in such a direction that the concentration of Cu2+(aq) ions in each half cell becomes the same eventually.

Which of the following statements concerning the set-up is correct?

A. The salt bridge allows electrons to flow from one half cell to the other. B. Oxidation occurs at Y. C. Electrons flow from Y to X in the external circuit. D. The mass of X will decrease but the mass of Y will increase.

Ans: D

88. 2007 Q24 Consider the redox reaction represented by the equation below:

2 S2O3 2 (aq) + I2(aq) S4O6 2 (aq) + 2 I (aq)

Which of the following statements is/are correct?

(1) The oxidation number of sulphur in S2O3 2 (aq) is +3. (2) One of the half equations of this reaction is 2 S2O3 2 (aq) S4O6 2 (aq) + 2 e . (3) I2(aq) is oxidised by S2O3 2 (aq) in the reaction.


Ans: C

28

89. 2007 Q36 The following diagram represents a chemical cell called fuel cell.

Hydrogen and oxygen are passed into the fuel cell. The half equations for the chemical changes occurring at electrode X and electrode Y are listed below:

at X: H2 + 2OH 2H2O + 2e at Y: O2 + 2H2O + 4 e 4OH

Which of the following statements concerning the fuel cell is correct? A. Reduction occurs at X. B. A current flows from X to Y through the external circuit. C. Both H2(g) and O2(g) function as fuels in the cell. D. The fuel cell is an environmentally-friendly chemical cell.

Ans: D

90. 2007 Q44 Which of the following statements concerning a zinc-carbon cell are correct?

(1) Manganese(IV) oxide acts as the anode (2) Ammonium chloride as an electrolyte (3) Zinc acts as the negative electrode


Ans: C

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91. 2007 Q45 Using carbon as electrodes, which of the following solutions would give hydrogen upon electrolysis?

(1) 1 M silver nitrate solution (2) 2 M sodium hydroxide solution (3) 3 M calcium chloride solution


Ans: D

92. 2007 Q46 Which of the following statements concerning the reaction of concentrated nitric acid with copper is/are correct?

(1) A colourless gas is evolved. (2) One mole of NO3 (aq) ions requires one mole of electrons for reduction. (3) It involves a displacement reaction.


Ans: B

93. 2008 Q4 Consider the ionic equation below :

OH 8 Snx 2MnHy Snx MnO2 2422

4 ++++++++

What is the value of x? A. 2 B. 4 C. 5 D. 7

Ans: C

30

94. 2008 Q5 In which of the following compounds is the oxidation number of nitrogen lowest? A. ClNH4 B. 2NaNO C. OHNH2

D. 23 )Pb(NO

Ans: A

95. 2008 Q11 In which of the following processes does sulphur dioxide act as a reducing agent? A. passing sulphur dioxide into water B. passing sulphur dioxide into iodine solution C. passing sulphur dioxide into iron(II) sulphate solution D. passing sulphur dioxide into sodium hydroxide solution

Ans: B

96. 2008 Q15

X and Z are metals. X reacts with Z 23 )NO( solution according to the following equation :

(s)(aq)(aq)(s) 22 ZXZX ++ ++

Which of the following deductions is correct? A. Both X and Z can react with water. B. The reactivity of Z is higher than that of X. C. X acts as a reducing agent in the reaction. D. Z acts as the negative pole when X and Z are used as electrodes in a chemical cell with sodium chloride solution as electrolyte.

Ans: C

97. 2008 Q23 Which of the following is / are related to the use of silver oxide cells in watches? (1) Silver oxide cells are rechargeable. (2) Silver oxide cells are small in size. (3) Silver is an expensive metal.

A. (1) only B. (2) only C. (1) and (3) only D (2) and (3) only

Ans: B

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98. 2008 Q36 Which of the following processes does NOT involves redox reaction(s)? A. bromination of methane B. electrolysis of sea water C. thermal decomposition of limestone D. removal of air pollutants in car exhaust by catalyst convertor

Ans: C

99. 2008 Q40 A compound is composed of element Z and hydrogen. Electrolysis of this compound under molten state

produces the same number of Z atoms at the cathode as hydrogen molecules at the anode. The following half equation shows the change occurring at the anode :

+ e 2HH2 2

What is the oxidation number of Z in the compound? A. 2 B. 1 C. 1+ D. 2+

Ans: D

100. 2008 Q44 The following diagram shows the set-up of a chemical cell.

Given that aq)(Br2 is a stronger oxidizing agent than (aq)Fe3+ , which of the changes represented by the following half equations would occur if the cell is producing a current?

(1) (aq)Fee(aq)Fe 23 ++ + (2) ++ + e(aq)Fe(aq)Fe 32 (3) + 2e(aq)Br(aq)Br2 2


Ans: B

32

101. 2008 Q48 Upon electrolysis, which of the following solutions would give hydrogen at carbon cathode and oxygen at

platinum anode? (1) very dilute sodium chloride solution (2) dilute copper(II) sulphate solution (3) concentrated potassium sulphate solution


Ans: C 102. 2009 Q2 In which of the following reactions does nitrogen exhibit three different oxidation numbers in the species

involved? A. NH4NO3 N2O +2H2O B. 8NH3 + 3Cl2 6NH4Cl+N2 C. Mg + 4HNO3 Mg(NO3)2 + 2NO2 +2H2O D. 3Cu + 8HNO3 3Cu(NO3)2 + 2NO + 4H2O

Ans: A

103. 2009 Q4 The table below shows whether displacement reaction occurs between metals W, X, Y and Z with their ions. represents that displacement reaction occurs, while x represents that displacement reaction does not occur.

W X Y Z W2+(aq) x X+(aq) Y2+(aq) x x Z+(aq) x x x

Which of the following is the strongest reducing agent? A. X B. X+ C. Z D. Z+

Ans: C

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104. 2009 Q8 105. 2009 Q9 Directions : Questions 104 and 105 refer to the following diagram.

104. Which of the following observations can be made in the above set-up? A. There is no observable change. B. Gas bubbles appear on the zinc plate. C. Gas bubbles appear on the copper plate. D. The sulphuric acid gradually turns blue.

Ans: B 105. What will occur when the circuit is closed? A. Both metal plates gradually dissolve. B. The sulphuric acid gradually turns blue. C. The hydrogen ions in the solution are reduced to hydrogen gas. D. Electrons flow from the copper plate to the zinc plate in the external circuit.

Ans: C

106. 2009 Q13 A drunken driver breathes into a device containing dichromate ions. The oxidation number of chromium

would change from A. +6 to +3. B. +3 to +6. C. +3 to +2. D. +2 to +3.

Ans: A

34

107. 2009 Q17 This question refers to the following micro-scale experiment.

Which of the following types of reaction is / are involved in the experiment? (1) redox reaction (2) neutralisation (3) thermal decomposition


Ans: A

108. 2009 Q24 Which of the following substances can react with acidified potassium permanganate solution?

(1) propene (2) potassium iodide solution (3) sodium sulphite solution


Ans: D

109. 2009 Q34 Which of the following would NOT occur when a zinc-carbon cell is supplying electricity?

A. Water is produced, B. Zinc case becomes thinner. C. Ammonium ions are consumed. D. Manganese compound is oxidised.

Ans: D

35

110. 2009 Q35 In an experiment of electroplating nickel on a copper object, which of the following combinations is correct?

Anode Cathode Electrolyte A. copper object nickel CuSO4(aq) B. copper object nickel NiSO4(aq) C. nickel copper object CuSO4(aq) D. nickel copper object NiSO4(aq)

Ans: B

111. 2009 Q42 Which of the following acids can react with silver ?

(1) dilute sulphuric acid (2) concentrated nitric acid (3) concentrated hydrochloric acid


Ans: B

112. 2009 Q44 In the electrolysis of a copper(II) sulphate solution using copper cathode and graphite anode, which of the

following would change ? (l) pH of the solution (2) colour of the solution (3) mass of the graphite anode

A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (l), (2) and (3)

Ans: A

113. 2009 Q47 Which of the following statements concerning the anodisation of an aluminium object are correct?

(1) The electrolyte used can be dilute sulphuric acid. (2) A layer of aluminium oxide is formed on the surface of the object. (3) The aluminium object should be connected to the negative terminal of the power supply.


Ans: A

36

114. 2010 Q9 In which of the following set-ups would the voltmeter display the greatest magnitude of voltage reading ?

Ans: C 115. 2010 Q11 In which of the following species does the underlined element have an oxidation number of +3 ? A. O3 B. H3PO4 C. NH4+ D. NO2

Ans: D 116. 2010 Q22 Which of the following statements concerning potassium and calcium is / are correct ? (1) The reducing power of potassium is stronger than that of calcium. (2) The hardness of potassium is higher than that of calcium. (3) The density of potassium is greater than that of calcium. A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only

Ans: A 117. 2010 Q24 Which of the following is / are redox reaction(s) ? (1) CH4 + Cl2 CH3Cl + HCl (2) 2CrO42- + 2 H+ Cr2O72- + H2O (3) 2 KNO3 2 KNO2 + O2


Ans: B

37

118. 2010 Q34 In an experiment to study the electrolysis of copper(II) sulphate solution, the set-up used is shown below :

Which of the following statements concerning the above experiment is correct ? A. Reduction occurs at X. B. Hydrogen gas is evolved at Y. C. The pH of the solution increases gradually. D. The colour of the solution remains unchanged.

Ans: D

119. 2010 Q36 Consider the experimental set-ups shown in the figures below :

In Figure 1, if the Cu is replaced by Y, which of the following statements is correct ? A. Chlorine gas will be evolved at Y. B. A solid will be deposited on the surface of Y. C. A greater magnitude of voltage will be recorded. D. Electrons will flow from X to Y through the external circuit.

Ans: C

120. 2010 Q47 Which of the following reagents can convert iron(II) ions to iron(III) ions ? (1) chlorine water (2) dilute nitric acid (3) potassium bromide solution A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3)

Ans: A

nss chemistry part 7 redox reactions chemical cells and electrolysis _mc

Documents

solution x

aqueous solution of

brown solution

metal x

ironii sulphate solution

sodium hydroxide solution

d compound x

following equations