A solution of CrO$$_5$$ in amyl alcohol has a ____colour

We need to determine the colour of CrO$$_5$$ dissolved in amyl alcohol.

Identify CrO$$_5$$.

CrO$$_5$$ (chromium pentoxide) is formed during the chromyl chloride test or when $$\text{H}_2\text{O}_2$$ is added to acidified dichromate solution. Its structure is $$\text{CrO(O}_2\text{)}_2$$ — chromium bonded to one oxide and two peroxide groups.

Determine the colour.

CrO$$_5$$ is an unstable blue compound in aqueous solution. When dissolved in amyl alcohol (or diethyl ether), the blue colour is stabilised and becomes more persistent.

This is a well-known confirmatory test for chromium — the characteristic blue colour of CrO$$_5$$ in organic solvents like amyl alcohol or ether.

The correct answer is Blue.