Question

Assertion: Change in colour of acidic solution of potassium dichromate by breath Is used to test trunk drivers.
Reason: change in colour is due to the complexation of alcohol with potassium dichromate.
(A) both assertion and reason are correct and the reason is the correct explanation of the assertion
(B) both assertion and reason are correct but the reason is not the correct explanation of the assertion
(C) assertion is correct but reason is incorrect
(D) assertion is incorrect but the reason is correct.

Answer 1

Hint: Acidified potassium dichromate solution is an orange solution which changes to green when the alcohol is oxidised. This can be used as a test for alcohols and only alcohols will show the orange to green colour change with acidified potassium dichromate solution.

Complete step by step answer:
We have been given that acidified potassium dichromate is used to test the drunk drivers,
Potassium dichromate ${{K}_{2}}C{{r}_ {2}} {{O}_ {7}} $, is a common inorganic chemical reagent, most commonly used as an oxidizing agent in various laboratory and industrial applications. As with all hexavalent chromium compounds, it is acutely and chronically harmful to health.
Change in colour of acidic solution of potassium dichromate by breath is used to test drunk drivers. This change in colour is due to the oxidation of alcohol with potassium dichromate to form acetic acid.

During this reaction, the reddish-orange dichromate ion changes colour to the green chromium ion when it reacts with the alcohol; the degree of the colour change is directly related to the level of alcohol in the exhaled air.
In an aqueous solution the colour change exhibited can be used to test for distinguishing aldehydes from ketones. Aldehydes reduce dichromate from the +6 to the +3-oxidation state, changing colour from orange to green. This colour change arises because the aldehyde can be oxidized to the corresponding carboxylic acid.
So, we can say that assertion is correct but reason is incorrect.
So, the correct answer is “Option C”.

Note: Potassium dichromate, is a common inorganic chemical reagent, most commonly used as an oxidizing agent in various laboratory and industrial applications. As with all hexavalent chromium compounds, it is acutely and chronically harmful to health.