11.4. The reactions of chlorine
A subsection of Chemistry, 9701, through 11. Group 17
Listing 10 of 290 questions
When dilute sulfuricacid is electrolysed, water is split into hydrogen and oxygen. 2H2O→ 2H2+ O2A current of x A is passed through the solution for 14.0minutes. 462 cm3 of hydrogen are produced at the cathode, measured under room conditions. Calculate the number of hydrogen molecules produced during the electrolysis.  number of hydrogen molecules = Calculate the total number of electrons transferred to produce this number of hydrogen molecules.  total number of electrons = Calculate the quantity of charge, in coulombs, of the total number of electrons calculated in .  quantity of charge = C Calculate the current, x, passed during this experiment.  x = A The standard entropies, S o, of three species are given in the table. species S o / J K–1 mol–1 H2O+70 H2+131 O2+205 Calculate ∆S o for the reaction 2H2O→ 2H2+ O2. ∆S o = J K–1 mol–1 ∆H o for the reaction 2H2O→ 2H2+ O2is +572 kJ mol–1. Calculate ∆G o for this reaction at 298 K. ∆G o = kJ mol–1 Predict the effect of increasing temperature on the spontaneity of this reaction. Explain your answer.
9701_w21_qp_41
THEORY
2021
Paper 4, Variant 1
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Pure water is a very poor conductor of electricity. However, when hydrogenchloride gas is dissolved in water, ions are formed and a current flows during electrolysis. HCl + aq → H++ Cl –The overall change after electrolysis is that hydrogenchloride gas is converted into hydrogen and chlorine. 2HCl → H2+ Cl 2When a current of 3.10 A is passed through the solution for Y minutes, 351 cm3 of chlorine are produced at the anode, measured under room conditions. Calculate the number of chlorine molecules produced during the electrolysis.  number of chlorine molecules = Calculate the total number of electrons transferred to produce this number of chlorine molecules.  total number of electrons = Calculate the quantity of charge, in coulombs, of the total number of electrons calculated in .  quantity of charge = C Calculate the time, Y, in minutes, for which the current flows.  Y = minutes The standard entropies, S o, of three species are given in the table. species S o / J K–1 mol–1 HCl +187 H2+131 Cl 2+223 Calculate ∆S o for the reaction 2HCl → H2+ Cl 2. ∆S o = J K–1 mol–1 ∆H o for the reaction 2HCl → H2+ Cl 2is +185 kJ mol–1. Calculate ∆G o for this reaction at 298 K. ∆G o = kJ mol–1 Predict the effect of increasing temperature on the spontaneity of this reaction. Explain your answer.
9701_w21_qp_42
THEORY
2021
Paper 4, Variant 2
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When dilute sulfuricacid is electrolysed, water is split into hydrogen and oxygen. 2H2O→ 2H2+ O2A current of x A is passed through the solution for 14.0minutes. 462 cm3 of hydrogen are produced at the cathode, measured under room conditions. Calculate the number of hydrogen molecules produced during the electrolysis.  number of hydrogen molecules = Calculate the total number of electrons transferred to produce this number of hydrogen molecules.  total number of electrons = Calculate the quantity of charge, in coulombs, of the total number of electrons calculated in .  quantity of charge = C Calculate the current, x, passed during this experiment.  x = A The standard entropies, S o, of three species are given in the table. species S o / J K–1 mol–1 H2O+70 H2+131 O2+205 Calculate ∆S o for the reaction 2H2O→ 2H2+ O2. ∆S o = J K–1 mol–1 ∆H o for the reaction 2H2O→ 2H2+ O2is +572 kJ mol–1. Calculate ∆G o for this reaction at 298 K. ∆G o = kJ mol–1 Predict the effect of increasing temperature on the spontaneity of this reaction. Explain your answer.
9701_w21_qp_43
THEORY
2021
Paper 4, Variant 3
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Data should be selected from Table3.1 in order to answer some parts of this question. Table 3.1 electrode reaction E o / V Cl 2 + 2e– 2Cl – +1.36 2HOCl + 2H+ + 2e– Cl 2 + 2H2O +1.64 Cl O– + H2O + 2e– Cl – + 2OH– +0.89 Sn4+ + 2e– Sn2+ +0.15 Sn2+ + 2e– Sn –0.14 V2+ + 2e– V –1.20 V3+ + e– V2+ –0.26 VO2+ + 2H+ + e– V3+ + H2O +0.34 VO2 + + 2H+ + e– VO2+ + H2O +1.00 Standard electrode potentials are measured under standard conditions. Describe the standard conditions used in the Sn4+ / Sn2+ half-cell. Complete the diagram below to show how E o (Sn4+ / Sn2+) can be measured experimentally. Your diagram should be fully labelled to identify all apparatus and substances.  Equal volumes of 1.0 mol dm–3 Sn2+and 1.0 mol dm–3 Cl –are mixed. Use relevant E o values to explain whether a reaction occurs between these two ions. Equal volumes of 1.0 mol dm–3 of Sn2+and acidified 1.0 mol dm–3 VO2+are mixed. Write an equation for the reaction that takes place in the resulting mixture. A solution of SnCl 2is electrolysed for a measured time using a steady current. A mass of 2.95 g of tin metal is produced at the cathode. Al 2O3is electrolysed for the same time by the same current. Calculate the mass of aluminium metal produced at the cathode. Give your answer to three significant figures. Show your working.  mass of aluminium metal = g 
9701_w22_qp_41
THEORY
2022
Paper 4, Variant 1
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Data should be selected from Table3.1 in order to answer some parts of this question. Table 3.1 electrode reaction E o / V Cl 2 + 2e– 2Cl – +1.36 2HOCl + 2H+ + 2e– Cl 2 + 2H2O +1.64 Cl O– + H2O + 2e– Cl – + 2OH– +0.89 Sn4+ + 2e– Sn2+ +0.15 Sn2+ + 2e– Sn –0.14 V2+ + 2e– V –1.20 V3+ + e– V2+ –0.26 VO2+ + 2H+ + e– V3+ + H2O +0.34 VO2 + + 2H+ + e– VO2+ + H2O +1.00 Standard electrode potentials are measured under standard conditions. Describe the standard conditions used in the Sn4+ / Sn2+ half-cell. Complete the diagram below to show how E o (Sn4+ / Sn2+) can be measured experimentally. Your diagram should be fully labelled to identify all apparatus and substances.  Equal volumes of 1.0 mol dm–3 Sn2+and 1.0 mol dm–3 Cl –are mixed. Use relevant E o values to explain whether a reaction occurs between these two ions. Equal volumes of 1.0 mol dm–3 of Sn2+and acidified 1.0 mol dm–3 VO2+are mixed. Write an equation for the reaction that takes place in the resulting mixture. A solution of SnCl 2is electrolysed for a measured time using a steady current. A mass of 2.95 g of tin metal is produced at the cathode. Al 2O3is electrolysed for the same time by the same current. Calculate the mass of aluminium metal produced at the cathode. Give your answer to three significant figures. Show your working.  mass of aluminium metal = g 
9701_w22_qp_43
THEORY
2022
Paper 4, Variant 3
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