A 20.0 cm3 mixture of CO, CH4 and He gases is exploded by an electric discharge at room temperature with excess of oxygen.

Question

A $20\cdot0 cm ^{3}$ mixture of $CO, CH _{4}$ and $He$ gases is exploded by an electric discharge at room temperature with excess of oxygen. The volume contraction is found to be $13.0 cm ^{3}$. A further contraction of $14.0 cm ^{3}$ occurs when the residual gas is treated with $KOH$ solution. Find out the composition of the gaseous mixture in terms of volume percentage.

Answer 1

SOLUTION : Suppose the volume of $CO =x mL , CH _{4}=y mL . He$ gas is inert in reaction.

Reactions :

Given, for contraction, $\frac{x}{2}+2 y=13 \ldots$ (I) for $CO _{2}, x+y=14$

From (I) and (II) $, x=10, y=4$; hence vol. of $He =6 mL$

$\%$ of $CO =\frac{10}{20} \times 100=50 \%, \%$ of $CH _{4}=20 \%, \%$ of $He =30 \%$.