CAIE A Level Chemistry 9701 · Electrochemistry
Hot concentrated aqueous potassium hydroxide reacts with iodine. The unbalanced equation for the reaction is shown.
Explain, using oxidation numbers, how the equation is balanced. In your answer, identify the oxidising agent and the reducing agent, state the oxidation number of iodine in using a Roman numeral, and explain why this reaction is an example of disproportionation.
7 marks, so the mark scheme is looking for about 7 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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