Question

When dil. $H_{2}S{O}_4$ is added to aqueous solution of potassium chromate, yellow colour of solution turns to orange colour. It indicates :

• A. chromate ions are reduced
• B. chromate ions are oxidized
• C. mono-centric complex is converted into dicentric complex
• D. oxygen gets removed from chromate ions

Answer 1

Answer: (B)

chromate ions are oxidized

When dil. $H_{2}S{O}_4$ is added to the yellow solution of $K_{2}Cr{O}_4$ yellow colour changes to orange red due to the formation of $K_2{Cr}_2{O}_7$.
$2K_{2}Cr{O}_4+H_{2}S{O}_4⟶K_2{Cr}_2{O}_7+K_{2}S{O}_4+H_{2}O$
Above reaction shows that the monocentric complex $\left(K_{2}Cr{O}_4\right)$ is converted into dicentric $\left(K_2{Cr}_2{O}_7\right)$ complex and it can be explained with the help of diagram.