JEE MAIN - Chemistry (2024 - 5th April Morning Shift - No. 22)
The heat of combustion of solid benzoic acid at constant volume is $$-321.30 \mathrm{~kJ}$$ at $$27^{\circ} \mathrm{C}$$. The heat of combustion at constant pressure is $$(-321.30-x \mathrm{R}) \mathrm{~kJ}$$, the value of $$x$$ is __________.
Answer
150
Explanation
$$\mathrm{C}_6 \mathrm{H}_5 \mathrm{COOH}(\mathrm{s})+\frac{15}{2} \mathrm{O}_2(\mathrm{~g}) \longrightarrow 7 \mathrm{CO}_2(\mathrm{~g})+3 \mathrm{H}_2 \mathrm{O}(\mathrm{I})$$
$$\begin{aligned} & \Delta \mathrm{H}=\Delta \mathrm{U}+\Delta \mathrm{n}_9 R T \\ & \Delta \mathrm{H}=-321.30-\frac{1}{2} \mathrm{R} \times 300 \end{aligned}$$
So, $$x=150$$
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