During the estimation of Mohr's: salt. by using potassium permanganate, on 'adding KMnO solution to acidified Mohr's salt solution, pink colour of permanganate vanishes and finally appears at the end point a. Give the chemistry of the reaction. b. Illustrate the oxidising property of '(KMnO)_(3)' in basic medium..

Explanation

a. During the estimation. .(KMnO)_(4). reacts with ferrous ion in acidic-medium and is converted to .(MnSO)_(+).. Here .(KMnO)_(4). is an oxidising agent, which undergoes reduction. .2 (KMnO)_(4)+8 (H)_(2) (SO)_(4)+10 (FeSO)_(4) rarr.
.(K), (SO)_(4)+2 (M) (nS) (O)_(4)+5 (Fe)_(3)(SO)_(4)_(3)+8 (H)_(2) (O).
Here .+7., oxidation state is converted to .+2. oxidation state, te. pink colour is changed. Colour finally appears due to the presence of excess .(KMnO)_(4^(*).
b. In .alkaline (basic.) medium .2 (KMnO)_(4) pm. .2 (KOH) div 2 (~K)_(2) (MnO)_(2)+(H)_(2) (O)+[(O)].
For example, in alkaline medium .(KMnO). oxidises iodides to, iodates. .(Kl)+2 (KMnO)_(4)+(H), (O) rarr 2 (MnO)_(2)+(KIO)+2 (KOH).