Give chemical reactions for the following observations: (i) Potassium permanganate is a good oxidising agent in basic medium. (ii) Inter-convertibility of chromate ion and dichromate ion in aqueous solution depends upon pH of the solution . (iii) Potassium permanganate is thermally unstable at 513 K

Question

$\begin{array}{1 1}(a)(i) MnO_4^{-} +H_2O +I^{-} \to 2MnO_2 +2OH^{-}+ IO_3^{-} (ii) CrO_4 ^{2-}+2H^{+} \underrightarrow{Acid \;pH <7}\qquad Cr_2O_7^{2-} +H_2O (iii) KMnO_4 \qquad \underrightarrow{\Delta 513K}\qquad K_2MnO_4 +MnO_2+O_2 \\(b)\; (i) 2MnO_4^{-} +H_2O +I^{-} \to 2MnO_2 +2H_2O^{-}+ IO_3^{-}(ii) 2CrO_3 ^{2-}+2H^{+} \underrightarrow{Acid \;pH <7}\qquad Cr_2O_7^{2-} +H_2O(iii) 2KMnO_4 \qquad \underrightarrow{\Delta 513K}\qquad K_2MnO_4 +MnO_2+O_2\\(c) (i) 2MnO_4^{-} +H_2O +I^{-} \to 2MnO_2 +2OH^{-}+ IO_3^{-}(ii) 2CrO_4 ^{2-}+2H^{+} \underrightarrow{Acid \;pH <7}\qquad Cr_2O_7^{2-} +H_2O(iii) 2KMnO_4 \qquad \underrightarrow{\Delta 513K}\qquad KMnO_4 +MnO+O_2\\(D)\;(i) 2MnO_4^{-} +H_2O +I^{-} \to 2MnO_2 +2OH^{-}+ IO_3^{-}(ii) 2CrO_4 ^{2-}+2H^{+} \underrightarrow{Acid \;pH <7}\qquad Cr_2O_7^{2-} +H_2O(iii) 2KMnO_4 \qquad \underrightarrow{\Delta 513K}\qquad K_2MnO_4 +MnO_2+O_2\end{array} $</span>