Question

The oxidation of oxalic acid by acidified $KMn{O}_4$ is an example of autocatalysis. It is due to which of the following?

• A. $S{O}_4^{2-}$
• B. $Mn{O}_4^{2-}$
• C. $M{n}^{2+}$
• D. $K^{\oplus }$

Answer 1

Answer: (C)

$M{n}^{2+}$

In the permanganate titration of oxalic acid in the presence of bench $H_{2}S{O}_4$ (acid medium), it is found that there is slow discharge of the colour of permanganate solution in the beginning but after sometime, the discharge of the colour becomes faster. This is due to the formation of $MnS{O}_4$ during the reaction which acts as a catalyst for the same reaction. Thus, $M{n}^{+2}$ is an "auto catalyst" for this reaction. This is an example of auto catalyst.