Question

When hydrogen peroxide is treated with a cold acidified $K_{2}C{r}_2{O}_7$ solution containing ether, blue colour is obtained. This is due to:

• A. perchromic acid
• B. potassium chromate
• C. chromium sulphate
• D. chromium trioxide

Answer 1

Answer: (A)

perchromic acid

The reaction betweeen $K_{2}2C{r}_2{O}_7$ (acidic field) and $H_2{O}_2$ is given as:

$K_{2}2C{r}_2{O}_7$ + $H_{2}S{O}_4+4H_2{O}_2$ $\to$ $2Cr{O}_5+K_{2}S{O}_4+5H_{2}O$

The deep blue colour obtained is due to formation of $Cr{O}_5$; which fades away and compound gets decomposed to $C{r}^{3+}$ and O${}_2$ (g) in the aqueous solution readily. So, ether is added to extract $Cr{O}_5$ because it will remain stable in such medium.