Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
The electrolysis of sodium chloride solution
19 practice questions
Practice questions
1–8 of 8 · Normal
Question 1
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 2
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 3
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 4
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 5
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 6
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 7
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 8
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.