Bryan Chong's answer to ok's Junior College 1 H2 Maths Singapore question.

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Bryan Chong
Bryan Chong's answer
15 answers (Tutor Details)
1st
I hope this helps, not too sure where the qn is going.

MnO4- reduces to different extents in solutions of different pH, see the redox reactions in your Data Booklet for references. In acidified solutions (higher [H+]), MnO4- reduces to Mn2+, hence being able to oxidise a larger number of Fe2+ ions. In a neutral solution, you will need more MnO4- solution to oxidise the same amount of FeSO4 as MnO4- oxidises to a smaller extent in neutral solutions.
O.N. of Mn in neutral solution: +4
O.N. of Mn in acidified soln: +2