Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Electrolysis
198 practice questions
Topics covered
- Why things conduct electricity17 practice questions
- Passing electricity through compounds: electrolysis20 practice questions
- The electrolysis of molten compounds19 practice questions
- Electrolysis and redox19 practice questions
- The electrolysis of other molten substances19 practice questions
- The electrolysis of aqueous solutions18 practice questions
- The electrolysis of sodium chloride solution19 practice questions
- The electrolysis of copper(ii) sulfate solution using inert electrodes18 practice questions
- The electrolysis of some other solutions using inert electrodes19 practice questions
- What would happen with non-electrolytes?19 practice questions
Practice questions
121–130 of 198
Question 121
2 marks · Normal
Answer and see the solution →During the electrolysis of sodium chloride solution, hydrogen gas is produced at the cathode rather than sodium metal.
Explain why sodium ions do not gain electrons at the cathode, but hydrogen ions do.
Question 122
4 marks · Normal
Answer and see the solution →In the electrolysis of sodium chloride solution, hydrogen gas forms at the cathode.
(a)[1 mark]State the ions present in sodium chloride solution that move to the cathode.
(b)[2 marks]Write a balanced half-equation to show the reaction occurring at the cathode. (You may use either half-equation involving H+ or H2O.)
(c)[1 mark]Explain, in one sentence, what happens to the electrons at the cathode during this reaction.
Question 123
3 marks · Normal
Answer and see the solution →During the electrolysis of sodium chloride solution, 0.1 mol of hydrogen gas is collected at the cathode.
Calculate the number of moles of hydroxide ions formed around the cathode by the time this hydrogen gas is collected.
Assume the half-equation at the cathode is:
Question 124
3 marks · Normal
Answer and see the solution →After setting up an electrolytic cell with sodium chloride solution, a student predicts sodium metal will be produced at the cathode.
Use your knowledge of reactivity and the process of electrolysis to explain why this prediction is incorrect.
Question 125
4 marks · Normal
Answer and see the solution →The table shows some possible half-equations for reduction at the cathode during the electrolysis of aqueous sodium chloride.
(a)[2 marks]Possible cathode half-equations Equation Product formed at cathode 2Na^+(aq) + 2e^- → 2Na(s) 2H^+(aq) + 2e^- → H2(g) 2H2O(l) + 2e^- → H2(g) + 2OH^-(aq) (b)[2 marks]Identify which equation(s) correctly represent the cathode reaction for the electrolysis of sodium chloride solution and explain your choice.
Question 126
1 mark · Normal
Answer and see the solution →During the electrolysis of sodium chloride solution, why does the solution near the cathode become alkaline?
- A.Hydrogen gas dissolves to form alkali.
- B.Sodium ions react with water to make sodium hydroxide.
- C.Hydroxide ions are produced at the cathode.
- D.Chlorine neutralises acid at the cathode.
Question 127
2 marks · Normal
Answer and see the solution →State two reasons why hydrogen is produced at the cathode, and not sodium, in the electrolysis of sodium chloride solution.
Question 128
4 marks · Normal
Answer and see the solution →Here are two possible half-equations for a reaction occurring at the cathode during electrolysis of sodium chloride solution:
(a)[1 mark]Name all ions present in the solution that could be reduced at the cathode.
(b)[2 marks]Which of the two half-equations shows the production of hydrogen gas from water? Explain your answer.
(c)[1 mark]Write a word equation for the cathode reaction using water as the starting material.
Question 129
2 marks · Hard
Answer and see the solution →Write a balanced half-equation, including state symbols, for the reduction that takes place at the cathode during the electrolysis of sodium chloride solution. State the physical state of each species involved.
Question 130
5 marks · Hard
Answer and see the solution →A student sets up an electrolytic cell using sodium chloride solution and collects the gases produced. They notice that the solution near the cathode becomes increasingly alkaline as the reaction proceeds.
(a)[1 mark]Name the ion that increases in concentration around the cathode.
(b)[2 marks]Write a balanced chemical equation, with state symbols, for the process at the cathode that explains this change.
(c)[2 marks]Explain why the solution near the cathode becomes alkaline as electrolysis continues. Relate your answer to the ions produced and removed at the electrode.