Question

121. The amount of ethyl alcohol in the blood of a person can be analyzed by using a breath analyzer which contains acidified ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$. Explain the principle involved.

Answer 1

• A breath analyzer is a device that is used to estimate blood alcohol concentration in a human body.
• It is based on a principle in which exhaled air passes through a mixture of chemicals containing Sulfuric acid $\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$, Potassium dichromate $\left({\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7\right)$, Silver nitrate $\left({\mathrm{AgNO}}_3\right)$, and water $\left({\mathrm{H}}_2\mathrm{O}\right)$.
• In this method, silver nitrate is used as a catalyst, and ethyl alcohol $\left({\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH}\right)$ in the presence of sulfuric acid turns potassium dichromate solution from orange to green due to the conversion of potassium dichromate into chromium sulfate ${\mathrm{Cr}}_2{\left({\mathrm{SO}}_4\right)}_3$.
• The intensity of the green color indicates the larger amount of ethyl alcohol in the exhaled air.