2500 cc of oxygen was burnt with 600 cc of ethane [C₂H₆]. Calculate the volume of unused oxygen and the volume of carbon dioxide formed.

[By Lussac's law]

$\begin{matrix} 2\text{C}$2\text{H}6 & + & 7\text{O}2 & \longrightarrow & 4\text{CO}2 & + & 6\text{H}_2\text{O} \ 2 \text{ vol.} & : & 7 \text{ vol.} & \longrightarrow & 4\text{ vol.} & : & 6\text{ vol.} \end{matrix}

To calculate the volume of unused oxygen.

$\begin{matrix} \text{C}$2\text{H}6 & : &\text{O}_2 \ 2 & : & 7 \ 600 & : & x \end{matrix}

Therefore,

$\dfrac{7}{2} \times 600 = x \\[0.5em] \Rightarrow x = 2100 \text{cc}$

Therefore, volume of unused oxygen = 2500 - 2100 = 400 cc

To calculate the volume of carbon dioxide formed

$\begin{matrix} \text{C}$2\text{H}6 & : & \text{CO}_2 \ 2 & : & 4 \ 600 & : & x \end{matrix}

Therefore,

$\dfrac{4}{2} \times 600 = x \\[0.5em] \Rightarrow x = 1200 \text{cc}$

Therefore, volume of carbon dioxide formed is 1200 cc