Question

Assertion$\left(A\right)$: In the reaction between potassium permanganate and potassium iodide, permanganate ions act as oxidising agent.
Reason$\left(R\right)$: Oxidation state of manganese changes from $+2$ to $+7$ during the reaction.

• A. Both $A$ and $R$ are false.
• B. Both $A$ and $R$ are true and $R$ is the correct explanation of $A$.
• C. $A$ is true but $R$ is false.
• D. Both $A$ and $R$ are true and $R$ is not the correct explanation of $A$.

Answer 1

The correct option is C $A$ is true but $R$ is false.

Assertion: In the reaction between potassium permanganate and potassium iodide,
permanganate ions act as oxidising agent.
Corresponding reaction:
$2Mn{O}_4^{-}+H_{2}O+I^{-}\to 2Mn{O}_2+2O{H}^{-}+I{O}_3^{-}$
Reaction taking place:
$2Mn{O}_4^{-}+H_{2}O+I^{-}$
$Mn=+7H=+1I=-1$
$O=-2O=-2$
$\downarrow$
$2Mn{O}_2+2O{H}^{-}+I{O}_3^{-}$
$Mn=+4O=-2I=+5$
$O=-2H=+1O=-2$
Here $Mn{O}_4^{-}$ is getting reduced to $Mn{O}_2(+7$ state to $+4$ state$)$, while $I^{-}$ is getting oxidised to $I{O}_3^{-}(-1$ to $+5$ state$)$.
Since $Mn{O}_4^{-}$ is oxidising $I^{-}$ to $I{O}_3^{-}(-1$ to $+5$ state$)$ and getting reduced itself, thus the permanganate ion is acting as an oxidising agent in the above reaction.

Reason: Oxidation state of manganese $\left(Mn\right)$ changes from $+2$ to $+7$ during the reaction.
Reaction taking place:
$2Mn{O}_4^{-}+H_{2}O+I^{-}\to 2Mn{O}_2+2O{H}^{-}+I{O}_3^{-}$
$Mn=+7H=+1I=-1Mn=+4O=-2I=+5$
$O=-2O=-2O=-2H=+1O=-2$
Here, $Mn{O}_4^{-}$ is getting reduced as oxidation state of $Mn$ is decreasing from+7 to +4, and I^− is getting oxidised as oxidation state of Iodine is increasing from $-1$ to $+5$.
Thus, the assertion is correct while the reason is incorrect.
Hence, correct answer is option $\left(C\right)$.