Why is not used to make the medium acidic in oxidation reactions of in an acidic medium?
(i) Both and act as oxidising agents.
(ii) oxidises into which is also an oxidising agent.
(iii) is a weaker oxidising agent than .
(iv) acts as a reducing agent in the presence of .
The answer is the option (ii). is oxidised by into which is also an oxidising agent. Since hydrochloric acid is oxidised to chlorine, permanganate titrations in their presence are unsatisfactory.