When hydrogen peroxide is added to acidified potassium dichromate, a blue colour is produced due to formation of `:`

Options

A. `(NH_(3)) CrO_(4)`
B. `K_(3)CrO_(8)`
C. `CrO_(5)`
D. `k[CrO(O_(2))(CH)]`

Answer

C

Explanation

The products depends on the pH and the concentration of Cr.
`Cr_(2)O_(7)^(2-) + 2H^(+) + 4H_(2)O_(2) rarr 2CrO(O_(2))_(2) + 5H_(2)O`
The deep blue-viole colored peroxo compound `CrO(O_(2))_(2)` or `CrO_(5)` decomposes rapidly in aqueous solution into `Cr^(3+)` and oxygen. In less acidic solutions `K_(2)Cr_(2)O_(7)` and `H_(2)O_(2)` give salts which are violet colored and diamagnetic. These contain `[CrO(O_(2)) OH]^(-)` . In alkaline solution with `30% H_(2)O_(2)` , red-brown compounds `K_(3)CrO_(8)` is formed which is a traperoxo species `[Cr(O_(2))_(4)]^(3-)`, and contains `Cr(+5)`. In ammonia solution, the dark red-brown compound `(NH_(3))_(3) CrO_(4)` is formed, it contains `Cr(+4)`.