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AIIMS 2006
Exam
AIIMS
Year
2006
Subject
Chemistry
Chapter
d and f Block Elements

AIIMS 2006 · Chemistry · d and f Block Elements

Assertion : Change in colour of acidic solution of potassium...

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

Options

  1. AIf both assertion and reason are true and reason is the correct explanation of the assertion
  2. BIf both assertion and reason are true but reason is not the correct explanation of the assertion
  3. CIf assertion is true, but reason is false
  4. DBoth assertion and reason are false statements.

Correct answer

C. If assertion is true, but reason is false

Step-by-step solution

Change in colour is due to the oxidation of alcohol with potassium dichromate. Oxidation of alcohols with K2Cr2O7\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7 in dilute H2SO4\mathrm{H}_2 \mathrm{SO}_4 (orange solution): Assertion : Change in colour of acidic solution of potassium dichromate by breath is used to test drunk drivers. Reason
K2Cr2O7\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7 in presence of dilute H2SO4\mathrm{H}_2 \mathrm{SO}_4 acts as an oxidising agent. It is converted into chromic sulphate which is green in colour. K2Cr2O7+4H2SO4→K2SO4+Cr2(SO4)3+4H2O+32O2 (orange) \begin{gathered} \mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7+4 \mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{K}_2 \mathrm{SO}_4+\mathrm{Cr}_2\left(\mathrm{SO}_4\right)_3+4 \mathrm{H}_2 \mathrm{O}+\frac{3}{2} \mathrm{O}_2 \\ \text{ (orange) } \end{gathered} (green)
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