Assertion : Change in colour of acidic solution of potassium dichromate by breath is used to test drunk drivers. Reason : Change in colour is due to the complexation of alcohol with potassium dichroma

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Assertion : Change in colour of acidic solution of potassium dichromate by breath is used to test drunk drivers. Reason : Change in colour is due to the complexation of alcohol with potassium dichromate.

TestHub · Accepted Answer

Change in colour is due to the oxidation of alcohol with potassium dichromate. Oxidation of alcohols with $K_{2} Cr_{2} O_{7}$ in dilute $H_{2} SO_{4}$ (orange solution):
$K_{2} Cr_{2} O_{7}$ in presence of dilute $H_{2} SO_{4}$ acts as an oxidising agent. It is converted into chromic sulphate which is green in colour. $K_{2} Cr_{2} O_{7} + 4 H_{2} SO_{4} \to K_{2} SO_{4} + Cr_{2} (SO_{4})_{3} + 4 H_{2} O + \frac{3}{2} O_{2} (orange)$ (green)

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