# The reaction that occurs in a breath analyser, a device used to determine the alcohol level in a person's blood stream is

Question:

The reaction that occurs in a breath analyser, a device used to determine the alcohol level in a person's blood stream isĀ

$2 \mathrm{~K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}+8 \mathrm{H}_{2} \mathrm{SO}_{4}+3 \mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O} \rightarrow 2 \mathrm{Cr}_{2}\left(\mathrm{SO}_{4}\right)_{3}+$

$3 \mathrm{C}_{2} \mathrm{H}_{4} \mathrm{O}_{2}+2 \mathrm{~K}_{2} \mathrm{SO}_{4}+11 \mathrm{H}_{2} \mathrm{O}$

If the rate of appearance of $\mathrm{Cr}_{2}\left(\mathrm{SO}_{4}\right)_{3}$ is $2.67 \mathrm{~mol}$ $\min ^{-1}$ at a particular time, the rate of disappearance of $\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}$ at the same time is_________ $\mathrm{mol} \mathrm{min}^{-1}$ (Nearest integer)

Solution:

$\left(\frac{\text { Rate of disappearance of } \mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}}{3}\right)$

$=\left(\frac{\text { Rate of appearance of } \mathrm{Cr}_{2}\left(\mathrm{SO}_{4}\right)_{3}}{2}\right)$

$\Rightarrow\left(\frac{2.67 \mathrm{~mol} / \min \times 3}{2}\right)=$ rate of disappearance of

$\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}$

$\Rightarrow$ Rate of disappearance of $\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}=4.005$ $\mathrm{mol} / \mathrm{min}$