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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 _______.
ChemistryThermodynamics (C)JEE MainJEE Main 2024 (05 Apr Shift 1)
Solution:
1651 Upvotes Verified Answer
The correct answer is: 150
$\begin{aligned} & \mathrm{C}_6 \mathrm{H}_5 \mathrm{COOH}(\mathrm{S})+\frac{15}{2} \mathrm{O}_2(\mathrm{~g}) \rightarrow 7 \mathrm{CO}_2(\mathrm{~g})+3 \mathrm{H}_2 \mathrm{O}(\ell) \\ & \Delta \mathrm{H}=\Delta \mathrm{U}+\Delta \mathrm{n}_{\mathrm{g}} \mathrm{RT} \\ & =-321.30-\frac{1}{2} \frac{\mathrm{R}}{100} \times 300 \\ & =(-321.30-150 \mathrm{R}) \mathrm{kJ}\end{aligned}$

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