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CAIE A Level Chemistry 9701 · Electrochemistry

Electrochemistry: compare question

Compare7 marksChallenge

Chlorine reacts with cold dilute aqueous sodium hydroxide to form sodium chlorate(I), NaClO, and sodium chloride.

(a) State the oxidation number of chlorine in NaClO, and write the Roman numeral that indicates the magnitude of this oxidation number.

(b) Explain why this reaction is an example of disproportionation, using changes in oxidation number.

(c) In a separate reaction, chlorine is bubbled into hot concentrated aqueous sodium hydroxide. The products are sodium chlorate(V), NaClOX3\ce{NaClO3}, and sodium chloride. Compare this reaction with the cold dilute reaction in terms of the oxidation number changes of chlorine and the oxidising and reducing behaviour of the chlorine.

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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.

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