20 ml. each of oxygen and hydrogen and 10 ml. of carbon monoxide are exploded in an enclosure. What will be the volume and composition of the mixture of the gases when they are cooled to room temperature.

Given,

20 ml. each of oxygen and hydrogen and 10 ml. of carbon monoxide

[By Lussac's law]

$\begin{matrix} 2\text{CO}& + & \text{O}$2 & \longrightarrow & 2\text{CO}2 & \ 2 \text{ vol.} & : & 1 \text{ vol.} & \longrightarrow & 2 \text{ vol.} & \ \end{matrix}

To calculate the amount of CO₂ produced,

$\begin{matrix} \text{CO}& : & \text{CO}_2 & \ 2 \text{ vol.} & : & 2 \text{ vol.} & \ 10 \text{ ml} & : & x \text{ ml} & \ \end{matrix}$

Therefore, CO₂ produced is 10 ml

To calculate the amount of O₂ used,

$\begin{matrix} \text{CO}& : & \text{O}_2 & \ 2 \text{ vol.} & : & 1 \text{ vol.} & \ 10 \text{ ml} & : & x \text{ ml} & \ \end{matrix}$

$\dfrac{1}{2} \times 10 = x \\[0.5em] \Rightarrow x = 5 \text{ ml}$

From relation,

$\begin{matrix} 2\text{H}$2 & + & \text{O}2 & \longrightarrow & 2\text{H}_2 \text {O} & \ 2 \text{ vol.} & : & 1 \text{ vol.} & \longrightarrow & 2 \text{ vol.} & \ \end{matrix}

$\begin{matrix} \text{H}$2 & : & \text{O}2 & \ 2 \text{ vol.} & : & 1 \text{ vol.} & \ 20 \text{ ml} & : & x \text{ ml} & \ \end{matrix}

$\dfrac{1}{2} \times 20 = x \\[0.5em] \Rightarrow x = 10 \text{ ml}$

Therefore, total vol. of oxygen used = 10 + 5 = 15 ml

Hence, oxygen left = 20 - 15 = 5 ml

Therefore, oxygen left is 5 ml and CO₂ produced is 10 ml.