Question

What is the oxidation state of Fe in the product formed when acidified potassium ferrocyanide $\left(K_4\right[Fe\left(CN{)}_6\right])$ is treated with hydrogen peroxide?

• A. $+2$
• B. $+3$
• C. $+1$
• D. $+6$

Answer 1

The correct option is B $+3$

When acidified potassium ferrocyanide $\left(K_4\right[Fe\left(CN{)}_6\right])$ reacts with hydrogen peroxide, it yields potassium ferricyanide $\left(K_3\right[Fe\left(CN{)}_6\right])$.

It is a redox reaction, which is described as follows:

$K_4\left[Fe{\left(CN\right)}_6\right]+H_{2}S{O}_4+H_2{O}_2\to K_3\left[Fe{\left(CN\right)}_6\right]+K_{2}S{O}_4+H_{2}O$

In this redox reaction,

$\text{2}Fe\left(II\right)-2e^{-}\to \text{2}Fe\left(III\right)$ (oxidation)

$\text{2}{O}^{-}\left(I\right)+2e^{-}\to \text{2}{O}^{-}\left(II\right)$ (reduction)

$K_4\left[Fe\right(CN{)}_6]$ acts as a reducing agent, whereas Hydrogen peroxide is a very strong oxidizing agent that oxidizes iron.

The oxidation state of Fe changes from +2 to +3.