Question

What changes occur when acidified $C{r}_2{O}_7^{2-}$ ion reacts with $H_2{O}_2$ solution in presence of ether solvent?

• A. Orange colour of solution turns blue
• B. Oxidation state of $Cr$ atom increases
• C. Oxidation state of $Cr$ atom remains constant
• D. Orange colour turns green

Answer 1

The correct option is A Orange colour of solution turns blue

When $H_2{O}_2$ is added to the acidified potassium dichromate solution (orange colour), the deep blue $Cr{O}_5$ is obtained.

$K_{2}C{r}_2{O}_7+H_{2}S{O}_4+4H_2{O}_2\to 2Cr{O}_5+K_{2}S{O}_4+5H_{2}O$
The deep blue colour fades away due to the formation of chromic sulphate. Oxygen is evolved in this process.

$4Cr{O}_5+6H_{2}S{O}_4\to 2C{r}_2(S{O}_4{)}_3+6H_{2}O+7O_2$