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
81–85 of 85 · Normal
Question 81
3 marks · Normal
Answer and see the solution →A student wants to find out whether substance X is an ionic compound, a covalent compound (non-electrolyte), or an acid using an experiment. She sets up the following experiment in which two carbon electrodes are placed in a solution of substance X, connected to a power supply and a bulb, as shown in the diagram:
Apparatus for testing conductivity. In three separate experiments she uses:
Test Substance in solution Observation A X dissolved in water Bulb does not light up B Molten X Bulb lights up C Aqueous acid Bulb lights up Using the data above, calculate whether substance X is ionic, covalent (non-electrolyte), or an acid. Explain your reasoning.
Question 82
6 marks · Normal
Answer and see the solution →Potassium iodide (KI) is an ionic compound. When heated until molten and electrolysed using inert electrodes, iodine gas is produced at one electrode and potassium metal at the other.
(a)[1 mark]State the ions present in molten potassium iodide.
(b)[1 mark]Write the half-equation for the reaction occurring at the cathode.
(c)[1 mark]Write the half-equation for the reaction occurring at the anode.
(d)[2 marks]State, in terms of electron transfer, which reaction involves reduction and which involves oxidation.
(e)[1 mark]Explain how you can use the mnemonic OILRIG to identify which reaction at the electrodes is oxidation and which is reduction.
Question 83
6 marks · Normal
Answer and see the solution →A student carries out the electrolysis of molten calcium chloride (CaCl2) in a laboratory using inert carbon electrodes.
(a)[2 marks]State what is meant by 'discharging an ion' during electrolysis.
(b)[1 mark]Identify the ions in molten calcium chloride and their movement during electrolysis.
(c)[1 mark]Write the half-equation for the discharge of chloride ions at the anode.
(d)[2 marks]Explain, using electron transfer, what happens to a calcium ion during electrolysis.
Question 84
6 marks · Normal
Answer and see the solution →A student sets up an electrolysis experiment using molten potassium iodide (KI). An external circuit with a bulb lights up when the current is switched on.
(a)[2 marks]State the ions present in molten potassium iodide. Identify which ions move towards the cathode and which move towards the anode during electrolysis.
(b)[1 mark]Write the ionic half-equation for the reaction occurring at the cathode.
(c)[1 mark]Write the ionic half-equation for the reaction occurring at the anode.
(d)[2 marks]For the electrode reaction at the cathode, state whether it is an oxidation or a reduction. Justify your answer using the concept of electron transfer.
Question 85
6 marks · Normal
Answer and see the solution →During the electrolysis of molten calcium chloride (CaCl2), calcium forms at one electrode and chlorine gas is released at the other.
(a)[2 marks]Write the balanced ionic half-equation for the reaction at the electrode where chlorine gas is produced.
(b)[2 marks]Explain what is meant by the term 'discharging an ion' using Ca^2+ or Cl^- as an example from this electrolysis process.
(c)[2 marks]Recall the meaning of the mnemonic OILRIG and use it to decide whether the reaction at the chlorine-producing electrode is an oxidation or a reduction.