When 5 litres of a gas mixture of methane and propane is perfectly combusted at $0°\mathrm{C}$ and 1 atmosphere, 16 litres of oxygen at the same temperature and pressure is consumed. The amount of heat released from this combustion in $\mathrm{kJ}\left({\mathrm{\Delta H}}_{\text{comb. }}\left({\mathrm{CH}}_4\right)=890 \mathrm{kJ}{ \mathrm{mol}}^{-1},{\mathrm{\Delta H}}_{\text{comb. }}\left({\mathrm{C}}_3{\mathrm{H}}_8\right)=2220 \mathrm{kJ}{ \mathrm{mol}}^{-1}\right)$is

Let volume of ${\mathrm{CH}}_4=\mathrm{x}$
Volume of ${\mathrm{C}}_3{\mathrm{H}}_8=(5-x)$
${\mathrm{CH}}_4+2{\mathrm{O}}_2\to {\mathrm{CO}}_2+2{\mathrm{H}}_2\mathrm{O}$
Volume of O2 for comburstion of ‘x’ liters. of CH₄
1 lit. of ${\mathrm{CH}}_4=2$ lit. of O₂
x lit. of CH4 = ?
O₂ V for combustion of ${\mathrm{CH}}_4=2\mathrm{x}$ Litre
${\mathrm{C}}_3{\mathrm{H}}_8^2+5{\mathrm{O}}_2\to 3{\mathrm{CO}}_2+4{\mathrm{H}}_2\mathrm{O}$
Volume of O2 for comburtion of (5–x) lits. of
$\begin{array}{l}{\mathrm{C}}_3{\mathrm{H}}_8.\\ 1\text{ lit. }{\mathrm{C}}_3{\mathrm{H}}_8=5\text{ lit of }{\mathrm{O}}_2\\ (5-x)\text{ lit. }=5(5-x)\text{ lit. }\end{array}$
Total volume of $O_2=2x+5(5-x)=16$
$\begin{array}{l}=2x+25-5x=16\\ =3x=9\\ x=3\text{ lit. }\end{array}$
Mixture contains 3 lit. CH₄ and 2 lit. C₃H₈ Total heat released = heat released from 3
lit. of CH4 + heat released from 2 lit. of C₃H₈ 
Heat released from CH₄ 
22.4 lits. = 890 KJ
3 lit. = ?
$=\frac{890\times 3}{22.4}$
Heat released from ${\mathrm{C}}_3{\mathrm{H}}_8$
$\begin{array}{l}22.4\text{ lit. = }2220\mathrm{kJ}\\ 2\text{ lit. }=?\\ =\frac{2220\times 2}{22.4}\end{array}$
Total heat released
$\begin{array}{l}=\frac{890\times 3}{22.4}+\frac{2220\times 2}{22.4}\\ =\frac{2670+4440}{22.4}=317\mathrm{kJ}\end{array}$