JEE MAIN - Chemistry (2023 - 25th January Evening Shift - No. 14)
28.0 L of CO$$_2$$ is produced on complete combustion of 16.8 L gaseous mixture of ethene and methane at 25$$^\circ$$C and 1 atm. Heat evolved during the combustion process is ___________ kJ.
Given : $$\mathrm{\Delta H_c~(CH_4)=-900~kJ~mol^{-1}}$$
$$\mathrm{\Delta H_c~(C_2H_4)=-1400~kJ~mol^{-1}}$$
Answer
847
Explanation
Let, Volume of C2H4 is x litre
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$$ \begin{aligned} &\Rightarrow 28=16.8+\mathrm{x} \\\\ &\mathrm{x}=11.2 \mathrm{~L} \\\\ &\mathrm{n}_{\mathrm{CH}_4}=\frac{\mathrm{PV}}{\mathrm{RT}}=\frac{1 \times 5.6}{0.082 \times 298}=0.229 \text { mole } \\\\ &\mathrm{n}_{\mathrm{C}_2 \mathrm{H}_2}=\frac{11.2}{0.082 \times 298}=0.458 \text { mole } \\\\ &\therefore \text { Heat evolved }=0.229 \times 900+0.458 \times 1400 \\\\ &=206.1+641.2 \\\\ &=847.3 \mathrm{~kJ} \end{aligned} $$
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