Question

A gas mixture $3.67\, L$ in volume contain $C _{2} H _{4}$ and $CH _{4}$ in proportion of $2: 1$ by moles and is at $25^{\circ} C$ and $1 \,atm$. If the $\Delta H _{ C }\left( C _{2} H _{4}\right)$ and $\Delta H _{ C }\left( CH _{4}\right)$ are $-1400$ and $-900 \,kJ /$ mol find heat evolved (in $kJ$ ) on burning this mixture.

Answer 1

There is $2.44\, L \,C _{2} H _{4} \longrightarrow n$
$=\frac{1 \times 2.44}{0.082 \times 298}=0.1\, mol$
there is $1.22 \,L \,CH _{4} \longrightarrow n$
$=\frac{1 \times 1.22}{0.082 \times 298}=0.05\, mol$
$\therefore$ Heat evolved
$=0.1 \times 1400+0.05 \times 900=185 \,kJ$.