Acidic dichromate ion reacts with hydrogen peroxide to give deep blue colour. This is due to the formation of

• A

  $\mathrm{CrO}(\mathrm{O})_2$
• Correct answer
  B

  $\mathrm{CrO}_5$
• C

  Both (a) and (b)
• D

  None of (a) and (b)

Solution

When cold $\mathrm{H}_2 \mathrm{O}_2$ is added in cold mixture of $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$ and conc. $\mathrm{H}_2 \mathrm{SO}_4$ (i.e. $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$ in acidic medium), a deep blue solution of blue perchromate is obtained as, $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7+\mathrm{H}_2 \mathrm{SO}_4 \longrightarrow \mathrm{~K}_2 \mathrm{SO}_4+\mathrm{H}_2 \mathrm{Cr}_2 \mathrm{O}_7$

Hence, the correct answer is option: 'B'.