Question

What is the number of coulombs required for the conversion of one mole of $Mn{O}_4^{-}$ to one mole of $M{n}^{2+}$?

• A. $5\times 96500$
• B. $3\times 96500$
• C. $96500$
• D. $9650$

Answer 1

Answer: (A)

$5\times 96500$

$Mn{O}_4^{-}$ is converted to $M{n}^{+2}$.

In $Mn{O}_4^{-}$, oxidation state of $Mn$ be $x.$

$x+4(-2)=-1,x-8=-1,x=+7.$

Oxidation state changes from $+7$ to $+2$.

Change in oxidation state $=5$.

$1$ Faraday ($96500$ coulombs) to change one oxidation state.

To change $5$ oxidation state, no. of coulombs required, $=5\times 1\text{Faraday}=5\times 96500\text{coulombs},$