Pearson Edexcel International GCSE in Chemistry · 4CH1 · Free · no account needed

Electrolysis — exam questions

11 original Incandio exam-style questions on electrolysis, 23 marks, about 23 minutes of writing. Each one carries the command word, the tariff and the specification statement it assesses, exactly as a paper presents them. This is an original Incandio practice question, written to reflect the structure and demands of the qualification. It is not an official Pearson Edexcel past-paper question.

This is the practice set for Electrolysis — the lesson that teaches it. Read the lesson first if the idea is new; come here when you want to find out whether you can turn it into marks. Completely free, no account needed to read.

What these questions ask of you

7 command words run through this set, and on Pearson Edexcel International GCSE Chemistry each one means something precise. Answering the wrong command is the commonest way a candidate who understands the lesson still loses the mark.

State what is meant by (1–2 marks)
the definition
Explain (2–4 marks)
the reason, in terms of particles, bonding, energy or equilibrium Misread as: describing the observation without giving the chemistry that causes it
Give (1–2 marks)
a short factual answer — the most common chemistry command
Suggest (1–3 marks)
a plausible answer applying taught chemistry to an unfamiliar substance
Identify (1–2 marks)
the correct substance or feature selected from what is given
Write (1–3 marks)
the equation, formula or ionic equation, balanced, with state symbols where asked
Describe (2–5 marks)
developed, linked statements of what happens or what is observed Misread as: giving one bare observation where the tariff asked for a developed account

Assessed on Paper 1 (4CH1/1C) and Paper 2 (4CH1/2C), against AO1, AO2, AO3.

Where these sit in the specification

Pearson Edexcel International GCSE Chemistry (4CH1) — statements 1.58 · 1.59 · 1.60. Incandio is aligned to this specification; it is not published by, endorsed by or affiliated with Pearson, and it reproduces none of Pearson's wording.

The 11 questions

Answer them on paper, then open the lesson's exam practice to have them marked. The mark scheme, the accepted and rejected answers and the annotated model answer are in Incandio and are not printed here — an answer beside its question is not practice.

  1. Molten lead(II) bromide, PbBr₂, is electrolysed using inert carbon electrodes. A silvery liquid forms at one electrode and a brown vapour at the other.

    (a)

    (1)Identify

    Identify the silvery liquid formed at the negative electrode.

    Molten lead(II) bromide, PbBr₂, is electrolysed using inert carbon electrodes. A silvery liquid forms at one electrode and a brown vapour at the other.

    Specification 1.59 · AO2 · about 1 min

    (b)

    (2)Write

    Write the half equation for the reaction at the negative electrode.

    Molten lead(II) bromide, PbBr₂, is electrolysed using inert carbon electrodes. A silvery liquid forms at one electrode and a brown vapour at the other.

    Specification 1.59 · AO2 · about 2 min

    (c)

    (2)Write

    Write the half equation for the reaction at the positive electrode.

    Molten lead(II) bromide, PbBr₂, is electrolysed using inert carbon electrodes. A silvery liquid forms at one electrode and a brown vapour at the other.

    Specification 1.59 · AO2 · about 2 min

    (d)

    (2)Explain

    Explain which of the two electrode reactions is oxidation and which is reduction.

    Molten lead(II) bromide, PbBr₂, is electrolysed using inert carbon electrodes. A silvery liquid forms at one electrode and a brown vapour at the other.

    Specification 1.59, 1.60 · AO1 + AO2 · about 2 min

    (Total for Question 1 = 7 marks)

  2. (1)State what is meant by

    State what is meant by an electrolyte.

    Specification 1.58 · AO1 · about 1 min

    (Total for Question 2 = 1 mark)

  3. (2)Explain

    Explain why solid lead(II) bromide does not conduct electricity but molten lead(II) bromide does.

    Specification 1.58 · AO1 · about 2 min

    (Total for Question 3 = 2 marks)

  4. (1)Give

    Give the name of the electrode at which reduction takes place.

    Specification 1.59 · AO1 · about 1 min

    (Total for Question 4 = 1 mark)

  5. (2)Explain

    Explain why the positive ions in an electrolyte move towards the negative electrode.

    Specification 1.59, 1.60 · AO1 + AO2 · about 2 min

    (Total for Question 5 = 2 marks)

  6. (2)Suggest

    Aluminium is extracted by electrolysing molten aluminium oxide rather than by heating it with carbon. Suggest why.

    Specification 1.60 · AO2 · about 2 min

    (Total for Question 6 = 2 marks)

  7. (3)Describe

    Describe what is observed at each electrode when concentrated aqueous sodium chloride is electrolysed.

    Specification 1.60 · AO1 · about 3 min

    (Total for Question 7 = 3 marks)

  8. (5)Describe

    Describe how a student could electrolyse molten lead(II) bromide safely and show which product forms at each electrode.

    Specification 1.58, 1.59, 1.60 · AO1 + AO2 + AO3 · about 5 min

    (Total for Question 8 = 5 marks)

Have them marked, then defend the answer

Practice tells you the mark; teaching it back tells you whether you understand it. On Incandio a topic counts as mastered only once you have taught it and defended it.

  1. Mark these questions — 11 questions, marked on Incandio against the authored scheme, with the mistake you actually made named.
  2. Teach it — explain electrolysis to Ember, an AI pupil who does not have it yet and asks the awkward question.
  3. Defend it — argue it against Michael Faraday over three rounds, marked against descriptors you can read first.

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