Question

Which one is correct for breath analyser used to test drivers suspected of drink?

• A. It works on the basis of redox reaction.
• B. The drunken drivers breath is allowed to pass through acidified $K_{2}C{r}_2{O}_7$ solution.
• C. The colour change of $K_{2}C{r}_2{O}_7$ solution is detected to test drunk level in breath.
• D. Alcohol vapours coming out with breath are oxidised to acetic acid in breath analyser.

Answer 1

Answer: (A), (B), (C), (D)

The correct options are
A The drunken drivers breath is allowed to pass through acidified $K_{2}C{r}_2{O}_7$ solution.
B It works on the basis of redox reaction.
C The colour change of $K_{2}C{r}_2{O}_7$ solution is detected to test drunk level in breath.
D Alcohol vapours coming out with breath are oxidised to acetic acid in breath analyser.

The chemical reaction inside the breath analyzer includes both oxidation and reduction. The breathalyzer contains a chamber with several compounds to support these reactions. They include potassium dichromate, sulfuric acid, silver nitrate.
The drunken driver's breath is allowed to pass through acidified $K_{2}C{r}_2{O}_7$ solution.
When the potassium dichromate solution in the breathalyzer reacts with ethanol, the potassium dichromate loses an oxygen atom.
This process is called reduction when a compound loses oxygen, gains hydrogen or gains (partially gains) electrons.
The reduction converts orange potassium dichromate into a green solution containing chromium sulfate.
At the same time, dichromate ion gets reduced to chromium ion and ethanol gets oxidized to acetic acid. Oxidation reactions often occur simultaneously with reduction reactions and are commonly abbreviated as redox reactions.
Hence, we can conclude that options A, B, C, and D are the correct options.