Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
The electrolysis of sodium chloride solution
19 practice questions
Practice questions
11–19 of 19
Question 11
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 12
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 13
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 14
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 15
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 16
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 17
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 18
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.
Question 19
2 marks · Hard
Answer and see the solution →Explain why sodium ions are not discharged at the cathode during the electrolysis of sodium chloride solution, whereas hydrogen is.