Electrolysis and redox
3 marks · NormalThe electrolysis of molten potassium chloride (KCl) produces potassium metal and chlorine gas.
Write the half-equation for the reaction at the cathode.
State whether the reaction at the cathode is oxidation or reduction.
Explain your answer to part (b) in terms of electron transfer.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) K^+ + e^- \rightarrow K
(b) Reduction
(c) Potassium ions gain electrons at the cathode.
Common mistakes: Mixing up oxidation and reduction at cathode.; Wrong sign in half-equation.; Not mentioning electrons in half-equation.
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Marking points
A1 (a) · 1 mark · Correct half-equation for potassium at the cathode: K^+ + e^- \rightarrow K
B1 (b) · 1 mark · Correctly identifies process as reduction.
M1 (c) · 1 mark · States potassium ions gain electrons / reduction is gain of electrons at the cathode.
Worked solution
The reaction is reduction because potassium ions gain electrons at the cathode.