3- Redox And Electrolysis(pp2)

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.1

85 Q.5 The element with an atomic number of 19 is likely to be A. B. C. D.

an oxidizing agent. a reducing agent. a non-metal. chemically unreactive.

85 Q.14 In which of the following substances does nitrogen have the lowest oxidation number? A. C.

NH4Cl HNO2

B. D.

NO2 N2

85 Q.15 MnO4 -(aq) + 8H + + xe - → Mn 2+(aq) + 4H2O(l) Which of the following statements about the above equation is correct? A. B. C. D.

The value of x is 6. 1 mole of MnO4 -(aq) produces 2 moles of Mn 2+(aq). The change in oxidation number of Mn is from -1 to +2. It represents a reduction reaction.

85 Q.40 A fork which is made of metal M can be silver-plated by the set-up shown below:

silver electrode

metal M

silver nitrate solution When a current has been passed through the solution for same time, which of the following will occur? (1) Silver ions will migrate to the silver electrode. (2) Silver ions will be reduced at the cathode. (3) The metal M will go into solution as ions. (4) The mass of the fork will increase. A. C.

(1) and (3) only (2) and (3) only

B. D.

(1) and (4) only (2) and (4) only

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.2

85 Q.41 In which of the following equations is the substance underlined acting as an oxidizing agent? (1) H2SO4 + BaCl2 → BaSO4 + 2HCl (2) Cu + 2AgNO3 → 2Ag + Cu(NO3)2 (3) SO2 + I2 + 2H2O → 2HI + H2SO4 (4) SO2 + 2H2S → S + 2H2O A. C.

(4) only (3) and (4) only

B. D.

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

Directions: Question 85 Q.53 and 85 Q.54 refer to the following diagrams. 85 Q.53 V electrode X

copper potassium chloride solution

Which of the following metals, when used as electrode X, would produce the largest reading on the voltmeter? A. C.

iron magnesium

B. D.

lead zinc

85. Q.54 If electrode X is zinc, which of the following statements concerning the cell is INCORRECT? A. B. C. D.

Electrons flow from electrode X to the copper electrode in the external circuit. Chlorine is given off at electrode X. Hydrogen is given off at the copper electrode. The mass of electrode X gradually decreases.

86 Q.1 The atomic structure of an element is: Number of electrons 17 Number of protons 17 Number of neutrons 19 In its compounds, this element is most likely to have an oxidation number of A. C.

+2 -1

B. D.

+1 -2

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.3

86. Q.6 aCl2 + 6OH - → bCl - + ClO3- + 3H2O When the above equation is balanced, the values for a and b should be: b 1 3 5 7

a 1 2 3 4

A. B. C. D. 86 Q.12

heat

(NH4)2Cr2O7 → N2 + 4H2O + Cr2O3 When ammonium dichromate is decomposed according to the above equation, which of the following correctly describes the changes in oxidation numbers of nitrogen and chromium? A. B. C. D.

Oxidation number of nitrogen Increases Increases Decreases Decreases

Oxidation number of chromium increases decreases increases decreases

86 Q.13 In the following reaction: 2I - + H2O2 + 2H + → I2 + H2O A. B. C. D.

I - is reduced and H + is oxidized. I - is reduced and H2O2 is oxidized. I - is oxidized and H2O2 is reduced. I - is oxidized and H + is reduced.

86 Q.14 If 0.1M aqueous solutions of the following compounds were electrolyzed using graphite electrodes, which one would give hydrogen at the cathode and oxygen at the anode? A. B. C. D.

copper(II) sulphate sodium hydroxide potassium iodide silver nitrate

86 Q.17 In which of the following reactions is sulphur dioxide acting as an oxidizing agent? A. B. C. D.

3SO2 + Cr2O72- + 2H + → 3SO42- + 2Cr 3+ + H2O SO2 + 2H2S → 3S + 2H2O SO2 + PbO2 → PbSO4 2SO2 + O2 → 2SO3

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.4

86 Q.20 In which of the following compounds does nitrogen have the lowest oxidation number? A. C.

HNO2 NO

B. D.

86 Q.33 Both molten lead(II) bromide and iron can conduct electricity. 1st statement A. True B. True C. True/False D. False

2nd statement True True False/True False

KNO3 NH3 They are both electrolytes.

2nd statement is a correct explanation of the 1st one. 2nd statement is NOT a correct explanation of the 1st one. Only ONE of the statements is true, the other is false. -----

86 Q.39 When aqueous copper(II) sulphate is electrolyzed using copper electrodes, the equation(s) for the reaction(s) which occur(s) at the anode is/are: (1) Cu(s) → Cu2+(aq) + 2e (2) Cu2+(aq) + 2e → Cu(s) (3) SO42-(aq) → SO2 + O2 + 2e A. C.

(1) only (1) and (2) only

86 Q.42

B. D.

(3) only (2) and (3) only

metal oxide

town gas

heat Which of the following metal oxides can be reduced by the method illustrated in the above diagram? (1) Fe2O3 (2) MgO (3) PbO A. C.

(2) only (1) and (2) only

B. D.

(3) only (1) and (3) only

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.5

87 Q.10 During electrolysis, electricity passes through the electrolyte as a result of the movement of A. C.

cations only. cations and anions.

B. D.

anions only. mobiles electrons.

87 Q.11 A iron

current metal X postaaium chloride solution

Referring to the above diagram, the largest current flowing from iron to metal X in the external circuit can be obtained when X is A. C.

copper. silver.

B. D.

magnesium. zinc.

87 Q.12 Tin plating can be used to prevent iron cans from rusting because A. B. C. D.

tin is higher than iron in the electrochemical series. the tin protects the iron from exposure to air. tin corrodes more readily than iron. the tin and the iron readily form an alloy which does not corrode.

87 Q.14 platium electrode X

platinum electrode Y

saturated sodium sulphate solution containing litmus

Referring to the above diagram, which of the following changes would occur when a current is passed through the solution for some time? A. Sodium is formed at X and sulphur dioxide is liberated at Y. B. Oxygen is liberated at X and hydrogen is liberated at Y. C. The colour of the solution around X and Y fades. D. The colour of the solution becomes blue around X and red around Y.

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.6

87 Q.39 In industry, graphite electrodes are always used in the electrolysis of concentrated sodium chloride solution because graphite (1) is cheap. (2) conducts electricity. (3) is chemically inert. (4) is a reducing agent. A. C.

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

B. D.

(2) and (4) only (2), (3) and (4) only

87 Q.42 Which of the following are redox reaction? (1) Mg(s) + CuSO4(aq) → MgSO4(aq) + Cu(s) (2) Al(OH)3(s) + NaOH(aq) → NaAlO2(aq) + 2H2O(l) (3) MnO2(s) + 4HCl(aq) → MnCl2(aq) + Cl2(g) + 2H2O(l) A. C.

(1) and (2) only (2) and (3) only

B. D.

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

87 Q.43 Which of the following statements is / are true for chlorine, bromine and iodine? (1) They exist as diatomic molecules at room temperature and pressure. (2) Their oxidizing power decreases as their relative molecular masses increase. (3) Their colours darken as their relative molecular masses increase. A. C.

(1) only (2) and (3) only

B. D.

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

88 Q.1 Which of the following statements concerning the Periodic Table is correct? A. In any group, the atomic size of the elements decreases with increasing atomic number. B. In any period, the metallic character of the elements increases with increasing atomic number. C. Group I elements are oxidizing agents and Group VII elements are reducing agents. D. The compounds formed between Group IV elements and other elements are mostly covalent. 88 Q.32 Potassium iodide solution turns brown on The iodide ions are reduced by chlorine to adding chlorine water. give iodine. 1st statement 2nd statement A. True True 2nd statement is a correct explanation of the 1st one. B. True True 2nd statement is NOT a correct explanation of the 1st one. C. True/False False/True Only ONE of the statements is true, the other is false. D. False False -----

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.7

88 Q.38 Which of the following metal oxides can be reduced by carbon? (1) magnesium oxide (2) iron(III) oxide (3) copper(II) oxide A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) 89 Q.10 A solution of silver nitrate was electrolyzed under a steady current, using silver electrodes. Which of the following graphs correctly represents the change in mass of the anode with time? B. A. Mass

Mass Time

Time D.

C.

Mass

Mass

Time

Time

89 Q.12 When a solution of magnesium sulphate of known concentration is electrolyzed using platinum electrodes, which of the following is a correct description of what happens? A. B. C. D.

Number of moles of Mg2+(aq) Number of moles of SO42-(aq) decreases decreases remains unchanged decreases decreases remains unchanged remains unchanged remains unchanged

89 Q.13 The anode of a dry cell is usually made of A. C.

zinc. tin.

B. D.

iron. lead.

pH value of the solution increases decreases remains unchanged remains unchanged

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.8

89 Q.14 In which of the following reactions is the underlined substance reduced? A. B. C. D.

Cu(OH)2(s) + 4NH3(aq) → [Cu(NH3)4](OH)2(aq) 2H+(aq) + CO32-(aq) → CO2(g) + H2O(l) Cl2(g) + 2Fe2+(aq) → 2Fe3+(aq) + 2Cl-(aq) 2Ag+(aq) + Zn(s) → 2Ag(s) + Zn2+(aq)

89 Q.29 During electrolysis, reduction occurs at the cathode. 1st statement A. True B. True C. True/False D. False

2nd statement True True False/True False

Cations gain electrons at the cathode.

2nd statement is a correct explanation of the 1st one. 2nd statement is NOT a correct explanation of the 1st one. Only ONE of the statements is true, the other is false. -----

89 Q.30 Magnesium is a stronger oxidizing agent than sodium. 1st statement A. True B. True C. True/False D. False

2nd statement True True False/True False

Mg2+ accepts electrons more readily than Na+(aq).

2nd statement is a correct explanation of the 1st one. 2nd statement is NOT a correct explanation of the 1st one. Only ONE of the statements is true, the other is false. -----

89 Q.38 K2Cr2O7(aq) + 3K2SO3(aq) + 4H2SO4(aq) → Cr2(SO4)3(aq) + 4K2SO4(aq) + 4H2O(l) In the above equation, which of the following oxidation number is / are changed? (1) Cr (2) S (3) O A. C.

(1) only (2) and (3) only

B. D.

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

90 Q.1 Which of the following elements in the third period of the Periodic Table is the strongest reducing agent? A. C.

sodium chlorine

B. D.

sulphur aluminium

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.9

90 Q.5 In going down the group VI elements of the Periodic Table, there is an increase in (1) the size of the atoms. (2) the melting point of the elements. (3) the oxidizing power of the elements. Which of the following combinations is correct? A. C.

(1) and (2) only (2) and (3) only

B. D.

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

90 Q.19 In which of the following pairs of substances is the oxidation number of the sulphur atom and the nitrogen atom the same A. C.

H2SO4 and HNO3 SCl2 and NO

B. D.

SO2 and HNO2 NaHSO4 and NH3

90 Q.23 A student tries to plate a copper ring with nickel using the set-up below: d.c. power supply electrolyte nickel rod copper ring Which of the following combinations is correct? A. B. C. D.

Anode Copper ring Nickel rod Copper ring Nickel rod

cathode nickel rod copper ring nickel rod copper ring

Electrolyte Ni2+(aq) Ni2+(aq) Cu2+(aq) Cu2+(aq)

90 Q.24 Which of the following pairs of metals would be expected to give the largest voltage when they are used as electrodes in a simple chemical cell using potassium nitrate solution as the electrolyte? A. C.

Zn and Pb Pb and Cu

B. D.

Mg and Ag Fe and Mg

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.10

Directions: Questions 91 Q.6 and 91 Q.7 refer to the following electrolysis experiment. 2M potassium sulphate solution

electrode X

electrode Y

91 Q.6 The gases collected at electrodes X and Y respectively are in the volume ratio of A. C.

1:1 1:4

B. D.

1:2 2:1

91 Q.7 Which of the following statements concerning the experiment is / are correct? (1) The pH value of the potassium sulphate solution remains unchanged at the end of the experiment. (2) The concentration of the potassium sulphate solution remains unchanged at the end of the experiment. (3) The products of electrolysis at electrodes X and Y would remain unchanged if 2M sulphuric acid were used instead of 2M potassium sulphate solution. A. C.

(1) only (1) and (3) only

91 Q.9

current metal X

metal Y

B. D.

(2) only (2) and (3) only

A wire filter paper soaked with sodium chloride solution

Which of the following combinations would produce the largest current flowing metal X to metal Y in the external circuit? metal X metal Y A. Fe Cu B. Mg Ag C. Ag Zn D. Cu Pb

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.11

91 Q.14 Sulphur dioxide is passed into a test-tube containing potassium dichromate solution acidified with dilute sulphuric acid. The colour of the solution gradually changes from orange to green. Which of the following statements concerning the above experiment is correct? A. B. C. D.

Sulphur dioxide is oxidized to sulphate. The green colour is due to the presence of Cr2+(aq) ions. The dilute sulphuric acid acts as a catalyst. The oxidation number of chromium changes from +7 to +2 in the reaction.

91 Q.43 Cl2(aq) + 2I-(aq) → I2(aq) + 2Cl-(aq) Which of the following statements concerning the above reaction are correct? (1) I-(aq) acts as a reducing agent. (2) Chlorine is a stronger oxidizing agent than iodine. (3) The reaction is a displacement reaction. A. C.

(1) and (2) only (2) and (3) only

B. D.

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

92 Q.4 Consider the following table: Element W X Atomic Number 9 10 Which of the following elements is likely to be oxidizing agent? A. C.

W Y

B. D.

X Z

Y 14

Z 19

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.12

Directions: Question 92 Q.9 and 92 Q.10 refer to the following diagrams: metal P

V

metal Q

V

metal P

metal R

sodium chloride solution

sodium chloride solution

cell voltage = +1.1 V

cell voltage = -1.1 V

metal P

V metal S

sodium chloride solution cell voltage = +1.5 V 92 Q.9 Which of the following represents the correct order of activity of the metals P, Q and R and S? A. C.

R, P, Q, S P, Q, S, R

B. D.

Q, P, R, S P, R, S, Q

92 Q.10 Which of the two metals used as electrodes would give the largest cell voltage? A. C.

Q and R S and R

B. D.

Q and S S and P

92 Q.12 Using 1 mole of reactant, which of the following chemical changes involves the highest number of electrons? A. CrO42-(aq) → Cr3+(aq) B. Cr2O72-(aq) → Cr3+(aq) C. MnO4-(aq) → Mn2+(aq) D. MnO42-(aq) → MnO2(s)

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.13

92 Q.37 Which of the following aqueous solutions, when electrolyzed using carbon electrodes, will liberate only gaseous products at both electrodes? (1) KOH(aq) (2) AgNO3(aq) (3) MgCl2(aq) A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) 92 Q.46 Sulphur dioxide is an oxidizing agent. 1st statement A. True B. True C. True/False D. False

2nd statement True True False/True False

Sulphur dioxide can decolorize bromine water.

2nd statement is a correct explanation of the 1st one. 2nd statement is NOT a correct explanation of the 1st one. Only ONE of the statements is true, the other is false. -----

93 Q.15 The oxidation number of copper remains unchanged when A. B. C. D.

magnesium ribbon is added to copper (II) sulphate solution. sodium carbonate solution is added to copper (II) nitrate solution. carbon is heated with copper (II) oxide. copper foil is burnt in chlorine.

93 Q.16 In which of the following equations does the underlined substance undergo reduction? A. B. C. D.

2H2O + 2K → 2KOH + H2 Fe2(SO4)3 + 2KI → 2FeSO4 + K2SO4 + I2 2H2S + SO2 → 3S + 2H2O NaClO + SO2 + H2O → NaCl + H2SO4

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.14

93 Q.17 current A copper electrode

electrode made of metal X

dilute sulphuric acid With reference to the above diagram, which of the following statements is correct? A. B. C. D.

The electrode made of metal X is the positive pole. Copper is at a higher position in the electrochemical series than metal X. The mass of the copper electrode decreases. The mass of the electrode made of metal X decreases.

93 Q.19 carbon electrode

carbon electrode

concentrated magnesium bromide solution In the above experiment, which of the following major products will be liberated at the electrodes? A. B. C. D.

cathode magnesium magnesium hydrogen hydrogen

anode oxygen bromine bromine oxygen

93 Q.24 There is gradual change in the properties of halogens from chlorine to iodine. Which of the following properties are in the order chlorine < bromine < iodine (1) oxidizing power (2) density (3) boiling point A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3)

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.15

94 Q.4 Both rubidium (Rb) and sodium are elements in Group I of the Periodic Table, but rubidium is more reactive than sodium. When a rubidium hydroxide solution is electrolyzed using platinum electrodes, hydrogen gas is liberated at the cathode. Which of the following statements is a correct explanation for the phenomenon described above? A. B. C. D.

The H+(aq) ion accepts an electron more readily than the Rb+(aq) ion. The H+(aq) ion is more mobile than the Rb+(aq) ion and migrates faster to the cathode. Rubidium is first liberated, but it reacts immediately with water to give hydrogen gas. The concentration of H+(aq) ions is higher than that of Rb+(aq) ions in the rubidium hydroxide solution.

94 Q.12 In which of the following experiments will a redox reaction occur? A. B. C. D.

adding copper turnings to iron (II) nitrate solution adding bromine water to potassium chloride solution adding iron filings to silver nitrate solution adding sodium chloride solution to silver nitrate solution

94 Q.13 When a substance X is electrolyzed using platinum electrodes, a gas is collected at each electrode. X may be A. B. C. D.

silver nitrate solution. potassium chloride solution. molten sodium chloride. molten copper (II) chloride

94 Q.17 In which of the following reactions does sulphur dioxide act as an oxidizing agent? A. B. C. D.

SO2 + 2Mg → 2MgO + S SO2 + 2KOH → K2SO3 + H2O SO2 + Cl2 + 2H2O → H2SO4 + 2HCl 5SO2 + 2KMnO4 + 2H2O → K2SO4 + 2MnSO4 + 2H2SO4

94 Q.34 Which of the following reagents can be used to distinguish between sodium sulphite solution and sodium sulphate solution? (1) barium chloride solution (2) acidified potassium permanganate solution (3) potassium iodide solution A. C.

(1) only (1) and (3) only

B. D.

(2) only (2) and (3) only

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.16

95 Q.10 In which of the following equations does the underlined substances become reduced? A. B. C. D.

CuSO4 + Zn → Zn SO4 + Cu 2FeCl2 + Cl2 → 2FeCl3 Pb(OH)2 + 2HNO3 → Pb(NO3)2 + 2H2O MgCO3 + 2HCl → MgCl2 + CO2 + H2O

95 Q.11 A student tries to electroplate an iron ring with nickel using the set-up shown below. d.c. supply

iron ring nickel rod solution X Which of the following combinations is correct? A. B. C. D.

Solution X Iron (II) sulphate solution Iron (II) sulphate solution Nickel (II) sulphate solution Nickel (II) sulphate solution

Anode Iron ring Nickel rod Iron ring Nickel rod

Cathode Nickel rod Iron ring Nickel rod Iron ring

95 Q.24 Consider the following equation. 2FeSO4.7H2O(x) → Fe2O3(y) + SO3(z) + SO2(g) + 14 H2O(l) Which of the following combinations is correct? A. B. C. D.

x aq aq s s

y s s aq s

z g l s g

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.17

95 Q.30 Which of the following statements is / are correct? (Refer to the following chemical equation) Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g) (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. C.

(1) only (1) and (3) only

B. D.

(2) only (2) and (3) only

95 Q.32 Astatine is a Group VII element below iodine in the Periodic Table. Which of the following statements concerning astitine is / are correct? (1) It is a liquid at room temperature and pressure. (2) It reacts with sodium to form an ionic compound. (3) It is a stronger oxidizing agent than iodine. A. C.

(1) only (1) and (3) only

B. D.

(2) only (2) and (3) only

95 Q.33 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. A. C.

(1) only (1) and (3) only

B. D.

(2) only (2) and (3) only

95 Q.37 In the set-up shown metal X is more reactive than metal Y. A

metal X

metal Y

lemon Which of the following statements concerning this set-up is / are correct? (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. A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.18

95 Q.40 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. C.

(1) and (2) only (2) and (3) only

B. D.

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

96 Q.7 V silver

metal

sodium nitrate solution Which of the following metals would produce the smallest voltage in the above set-up A. C.

iron copper

B. D.

aluminium magnesium

96 Q.25 step 1 N2

step 2 NH3

step 3 NO

step 4 NO2

HNO3

Which step in the above flow chart involves the largest change in oxidation number of nitrogen? A. C.

step 1 step 3

B. D.

step 2 step 4

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.19

96 Q.27 V lead electrode

magnesium electrode

salt bridge

1M lead (II) nitrates solution

1M magnesium nitrate solution

Which of the following statements concerning the above set-up is correct? A. B. C. D.

Electrons flow from the 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.

Directions: 96 Q.30 and Q.31 refer to the following experiment. gas Y

gas X

concentrated sodium chloride solution containing phenolphthalein

electrode

electrode

96 Q.30 Which of the following combinations is correct? A. B. C. D.

Gas X chlorine chlorine hydrogen oxygen

Gas Y hydrogen oxygen chlorine hydrogen

96 Q.31 Which of the following statements concerning the above experiment is / are correct? (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. A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.20

96 Q.35 In which of the following process 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 A. C.

(1) only (1) and (3) only

B. D.

(2) only (2) and (3) only

96 Q.42 X is element. It can form a cation X2+ which has an electronic arrangement 2,8,8. Which of the following statements concerning X are correct? (1) X is a strong oxidizing agent. (2) X is in Period 4 of the Periodic Table. (3) X burns in oxygen with a brick red flame. A. C.

(1) and (2) only (2) and (3) only

B. D.

96 Q.46 Zinc-carbon dry cells are rechargeable. 1st statement A. True B. True C. True/False D. False

2nd statement True True False/True False

(1) and (3) only (1), (2) and (3) The electrolyte used in zinc-carbon dry cells is potassium hydroxide.

2nd statement is a correct explanation of the 1st one. 2nd statement is NOT a correct explanation of the 1st one. Only ONE of the statements is true, the other is false. -----

97 Q.4 Which of the following statements concerning the elements in the third period of the Periodic Table is correct? A. Both sulphur and chlorine can be reduced by aqueous sodium sulphite. B. Magnesium is a stronger reducing agent than sodium. C. Phosphorus and chlorine form a covalent compound. D. Magnesium burns in oxygen to form an acidic oxide. 97 Q.7 During the electrolysis of 1M copper (II) chloride solution using copper electrodes, which of the following changes would occur at the electrodes? Anode Cathode A. hydrogen liberated chlorine liberated B. copper deposited chlorine liberated C. copper dissolved copper deposited D. copper deposited copper dissolved

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.21

97 Q.8 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) 97 Q.11 V

carbon rod

moist paste of ammonium chloride

zinc case

manganese (IV) oxide and carbon powder

A zinc-carbon cell is connected to a voltmeter as shown in the above diagram. Which of the following concerning the set-up is INCORRECT? 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. 98 Q.21 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 X to electrode Y in the external circuit. C. Carbon electrodes are used because they are chemically inert. D. The half equation for the change occurring at electrode Y is Fe2+ + 2e → Fe

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.22

98 Q.22 In which of the following reactions does the underlined substance act as a reducing agent ? A. B. C. D.

SO2 + 2H2S → 3S + 2H2O Pb(NO3)2 + H2SO4 → PbSO4 + 2HNO3 2HCl + MgO → MgCl2 + H2O 2KBr + Cl2 → 2KCl + Br2

98 Q.27 Consider the following chemical equation : Zn + pMnO2 + qNH4+ → Zn2+ + xMn2O3 + yNH3 + zH2O Which of the following combinations is correct ? A. B. C. D.

x 1 1 2 2

y 2 3 3 2

z 1 2 2 3

99 Q.9 In which of the following reactions is the underlined reactant reduced? A. B. C. D.

Cu2+ + 2OH- → Cu(OH)2 SO2 + 2Mg → 2MgO + S 2NH3 + 3CuO → 3Cu + N2 + 3H2O Zn + 2AgNO3 → Zn(NO3)2 + 2Ag

99 Q.12 Consider the electrolysis experiment shown below:

Which of the following statements concerning this experiment is correct ? A. B. C. D.

The mass of the impure copper rod deceases. 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.

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.23

99 Q.21 Consider the following chemical equation: 2HNO3 + xFeSO4 + yH2SO4 → zFe2(SO4)3 + 4H2O + 2NO Which of the following combinations is correct ? A. B. C. D.

x 2 4 6 6

y 1 3 2 3

z 1 2 3 3

99 Q.33 Which of the following reactions will occur when aluminium powder is added to silver nitrate solution ? (1) displacement (2) anodization (3) redox A. C.

(1) only (1) and (3) only

B. D.

(2) only (2) and (3) only

99 Q.36 The equation below represents the reaction of chlorine with hot concentrated potassium hydroxide solution: 3Cl2(g) + 6KOH(aq) → 5KCl(aq) + KClO3(aq) + 3H2O(ℓ) 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 -1. (3) The oxidation number of chlorine changes from 0 to +5. A. C.

(1) only (1) and (3) only

B. D.

(2) only (2) and (3) only

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.24

99 Q.40 Consider the following chemical cell:

Which of the following changes would lead to an increase in the voltage of the cell ? (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. A. C.

(1) only (1) and (3) only

B. D.

(2) only (2) and (3) only

99 Q.42 Consider the following experiment:

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

(1) and (2) only (2) and (3) only

B. D.

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

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.25

00 Q.5 Which of the following gases are the major products liberated in the electrolysis of concentrated sodium chloride solution using carbon electrodes? Cathode Hydrogen Chlorine Hydrogen Oxygen

A. B. C. D.

Anode Chlorine Hydrogen Oxygen Hydrogen

00 Q.28 Which of the following changes is NOT a redox reaction ? A. B. C. D.

Fe2(SO4)3 + H2S → 2FeSO4 + S + H2SO4 2Al + 6HCl → 2AlCl3 + 3H2 CaCO3 + CO2 + H2O → Ca(HCO3)2 2KClO3 → 2KCl + 3O2

00 Q.30 In which of the following substances does nitrogen has the smallest oxidation number ? A. B. C. D.

NH3 NO N2O N2

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.26

00 Q.35 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 X increases. (3) The salt bridge allows electrons to flow from one electrode to the other electrode. A. C.

(1) only (1) and (3) only

B. D.

(2) only (2) and (3) only

00 Q.43 Which of the following statements concerning a zinc-carbon cell are correct ? (1) The ammonium chloride in the cell acts as an electrolyte. (2) The manganese(IV) oxide in the cell acts as an oxidizing agent. (3) The zinc case of the cell acts as the positive terminal. A. C.

(1) and (2) only (2) and (3) only

B. D.

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

01 Q.8 Which of the following statements concerning the formation of chloride ions from chlorine atoms is correct ? A. B. C. D.

The number of shells occupied by electrons in a chlorine atom equals that in a chloride ion. The atomic number of chlorine increases by 1. The mass number of chlorine increases by 1. The change is an oxidation.

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.27

01 Q.22 Which of the following equations represents a redox reaction ? A. B. C. D.

NH4+(aq) + OH-(aq) → NH3(g) + H2O(l) 2CrO42-(aq) + 2H+(aq) → Cr2O7 2-(aq) + H2O(l) 2FeSO4(s) → Fe2O3(s) + SO3(g) + SO2(g) 2NaHCO3(s) → Na2CO3(s) + H2O(l) + CO2(g)

01 Q.24 Consider the half equation : IO3-(aq) + xH2O(l) + ye- → I-(aq) + zOH-(aq) Which of the following combinations is correct ? x 1 2 3 4

A. B. C. D.

y 2 4 6 8

z 2 4 6 8

01 Q.29 The oxidation number of lead in [Pb(OH)4]2-is A. C.

-2. +4.

B. D.

+2. +6.

01 Q.44 Consider the set-up shown below:

Which of the following statements are correct ? (1) The solution around electrode X turns brown. (2) The mass of electrode X remains unchanged. (3) Reduction occurs at electrode Y. A. (1) and (2) only B. C. (2) and (3) only D.

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

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.28

Directions: 98 Questions 4 and 5 refer to the following experiment: The circuit shown below is set up and the solid lead(II) bromide is heated until it becomes molten.

98 Q.4 Which of the following statements concerning the experiment is INCORRECT? A. B. C. D.

The bulb lights up. A reddish brown gas is liberated at electrode X Electrodes X and Y can be made of nichrome Oxidation occurs at electrode Y.

98 Q.5 Which of the following can be deduced from the experimental results? A. B. C. D.

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.

98 Q.21 Consider the following experiment. Which of the following statements concerning the above experiment is correct?

A. B. C. D.

Permanganate ions migrate into the salt bridge. Electrons flow from electrode 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

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.29

98 Q.22 In which of the following reactions does the underlined substance act as a reducing agent? A. B. C. D.

SO2 + Pb(NO3)2 2HCl + 2KBr +

2H2S → 3S + 2H2O + H2SO4 → PbSO4 + 2HNO3 MgO → MgCl2 + H2O Cl2 → 2KCl + Br2

98 Q.27 Consider the following chemical equation: Zn + pMnO2 + qNH4+ → Zn2+ + xMn2O3 + yNH3 + zH2O Which of the following combinations is correct? X y A. 1 2 B. 1 3 C. 2 3 D. 2 2

z 1 2 2 3

99 Q.6 The concentration of an aqueous solution of an acid is 1.0 m. 25.0 cm3 of this acid solution requires 37.5 cm3 of 2.0 M sodium hydroxide solution for complete neutralization. What is the basicity of the acid? A. C.

1 3

B. D.

2 4

99 Q.12 Consider the electrolysis experiment shown below:

Which of the following statements concerning this experiment is correct? A. B. C. D.

The mass of the impure copper rod deceases. 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.

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.30

99 Q.40 Consider the following chemical cell:

Which of the following changes would lead to an increase in the voltage of the cell? (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. A. C.

(1) only (1) and (3) only

B. D.

(2) only (2) and (3) only

00 Q.5 Which of the following gases are the major products liberated in the electrolysis of concentrated sodium chloride solution using carbon electrodes? A. B. C. D.

Cathode hydrogen chlorine hydrogen oxygen

Anode chlorine hydrogen oxygen hydrogen

00 Q.28 Which of the following changes is NOT a redox reaction? A. B. C. D.

Fe2(SO4)3 2Al + CaCO3 2KClO3

+ H2S 6HCl → + CO2 → 2KCl

→ 2FeSO4 + S + H2SO4 2AlCl3 + 3H2 + H2O → Ca(HCO3)2 + 3O2

00 Q.30 In which of the following substances does nitrogen has the smallest oxidation number? A. C.

NH3 N2O

B. D.

NO N2

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.31

00 Q.35 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 X increases. (3) The salt bridge allows electrons to flow from one electrode to the other electrode. A. C.

(1) only (1) and (3) only

B. D.

(2) only (2) and (3) only

00 Q.43 Which of the following statements concerning a zinc-carbon cell are correct? (1) The ammonium chloride in the cell acts as an electrolyte. (2) The manganese(IV) oxide in the cell acts as an oxidizing agent. (3) The zinc case of the cell acts as the positive terminal. A. C.

(1) and (2) only (2) and (3) only

B. D.

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

01 Q.6 When potassium carbonate solution and calcium chloride solution are mixed, calcium carbonate is precipitated. Which of the following mixtures would produce the greatest amount of precipitate? A. B. C. D.

5cm3 of 1 M K2CO3(aq) + 15 cm3 of 1 M CaCl2(aq) 10 cm3 of 1 M K2CO3(aq) + 10 cm3 of 1 M CaCl2(aq) 15 cm3 of 1 M K2CO3(aq) + 8 cm3 of 1 M CaCl2(aq) 18 cm3 of 1 M K2CO3(aq) + 5 cm3 of 1 M CaCl2(aq)

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.32

01 Q.11 Which of the following pairs of solutions, when mixed, would produce a precipitate? A. B. C. D.

lead(II) nitrate and sodium hydroxide copper(II) sulphate and sodium nitrate zinc chloride and potassium nitrate iron(II) sulphate and acidified potassium permanganate

01 Q.19 Consider the half equations of a redox reaction: 8H+(aq) + MnO4-(aq) + 5e- → Mn2+(aq) + 4H2O(l) C2O42-(aq) → 2CO2(g) + 2eHow many moles of MnO4-(aq) ions will react completely with one mole of C2O42-(aq) ions? A. C.

0.4 2.5

B. D.

1.0 5.0

01 Q.22 Which of the following equations represents a redox reaction? A. B. C. D.

NH4+(aq) + OH-(aq) → NH3(g) + H2O(l) 2CrO42-(aq) + 2H+(aq) → Cr2O7 2-(aq) + H2O(l) 2FeSO4(s) → Fe2O3(s) + SO3(g) + SO2(g) 2NaHCO3(s) → Na2CO3(s) + H2O(l) + CO2(g)

01 Q.23 Phosphoric acid is a tribasic acid with formula H3PO4. Which of the following formulae is INCORRECT? A. C.

CaH2PO4 (NH4)2HPO4

B. D.

01 Q.24 Consider the half equation: IO3-(aq) + xH2O(l) + ye- → I-(aq) + zOH-(aq) Which of the following combinations is correct? A. B. C. D.

x 1 2 3 4

y 2 4 6 8

z 2 4 6 8

Mg3(PO4)2 Na2HPO4

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.33

01 Q.29 The oxidation number of lead in [Pb(OH)4]2-is A. C.

–2 +4

B. D.

+2 +6

01 Q.44 Consider the set-up shown below:

Which of the following statements are correct ? (1) (2) (3) A. C.

The solution around electrode X turns brown. The mass of electrode X remains unchanged. Reduction occurs at electrode Y.

(1) and (2) only (2) and (3) only

B. D.

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

02 Q.10 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 Z A. carbon silver silver nitrate solution B. Zinc magnesium magnesium sulphate solution C. carbon carbon copper(II) sulphate solution D. Zinc carbon silver nitrate solution

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.34

02 Q.13 Which of the following equations represents a redox reaction? A. B. C. D.

Ca(HCO3)2 + 2HCl → CaCl2 + 2CO2 + 2H2O PCl3 + Cl2 → PCl5 Fe3+ + 3OH- → Fe(OH)3 Al2O3 + 2NaOH → 2NaAlO2 + H2O

02 Q.18 The symbol of vanadium is V. What is the oxidation number of vanadium in NH4VO3? A. C.

-1 +5

B. D.

+3 +6

02 Q.47 During electrolysis, oxidation takes place Cations accept electrons and are discharged at the cathode. at the cathode. 1st statement 2nd statement A. True True 2nd statement is a correct explanation of the 1st one. B. True True 2nd statement is NOT a correct explanation of the 1st one. C. True/False False/True Only ONE of the statements is true, the other is false. D. False False ----03 Q.3 When a small piece of calcium metal is put into a trough of water, a reaction occurs. Which of the following statements concerning this reaction is correct? A. C.

It is an endothermic reaction. A slight explosion occurs.

B. D.

It is a redox reaction. The calcium metal burns spontaneously in water.

03 Q.5 Which of the following methods can be used to obtain aluminium from aluminium oxide? A. C.

reducing the oxide with carbon electrolysis of the molten oxide

B. D.

heating the oxide strongly heating the oxide with iron powder

03 Q.15 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 electroysis is correct? A. B. C. D.

The concentration of Cu2+(aq) ions in the solution remains unchanged. The concentration of H+(aq) ions in the solution increases. O2(g) is liberated at the anode. H2(g) is liberated at the cathode.

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.35

03 Q.16 Which of the following conversions is NOT a reduction? A. B. C. D.

Fe2O3 → Fe Cu(OH)2 → CuO CH3COOH → CH3CH2OH H2SO4 → SO2

03 Q.18 Consider the following information about three elements, X, Y and Z. Element X Y Z

Atomic number 12 16 17

Which of the following statements concerning X, Y and Z is correct? A. B. C. D.

X reacts with Z to form an ionic compound. Y is a stronger oxidizing agent than Z. X has a simple molecular structure. Y can conduct electricity in the molten state.

03 Q.24 What is the oxidation number of sulphur in H2S2O7? A. C.

+2 +6

B. D.

+4 +8

03 Q.35 Which of the following is/are advantage(s) of using alkaline manganese cells over sinc- 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. A. C.

(1) only (1) and (3) only

B. D.

(2) only (2) and (3) only

Redox and electrolysis / Section 3 / Sect3pp.doc / S. W. Tse / P.36

M.C. Answer 85 5 14 15 40 41 53 54

94 4 12 13 17 34

03 3 5 15 16 18 24 35

B A D D A C B

A C B A B

86 1 6 12 13 14 17 20 33 39 42

95 10 11 24 30 32 33 37 40

C C B C B B D C A D

A D D B B D B C

87 10 11 12 14 39 42 43

96 7 25 27 30 31 35 42 46

C B B D C B D

C B D A D C C D

88 1 32 38

97 4 7 8 11

D C C

C D B D

89 10 12 13 14 29 30 38

98 4 5 21 22 27

C D A D A C B

B C C D A

90 1 5 19 23 24

99 6 12 40

A A C B B

C A A

91 6 7 9 14 43

00 5 28 30 35 43

B C C A D

A C A B A

92 4 9 10 12 37 46

01 6 11 19 22 23 24 29 44

A A C B B B

B A A C A C B D

93 15 16 17 19 24

B C D C C

02 10 13 18 47

D B C C