The difference between enthalpies of reaction at constant pressure and constant volume for the react — Thermodynamics and Thermochemistry Chemistry Question
Question
The difference between enthalpies of reaction at constant pressure and constant volume for the reaction:<br>$2\text{C}_6\text{H}_6\text{(l)} + 15\text{O}_2\text{(g)} \to 12\text{CO}_2\text{(g)} + 6\text{H}_2\text{O(l)}$<br>at 298 K in kJ is
Answer: A
💡 Solution & Explanation
$\Delta H - \Delta U = \Delta n_g RT$. The change in gaseous moles $\Delta n_g = 12 - 15 = -3$. $\Delta H - \Delta U = -3 \times 8.314 \times 10^{-3}\text{ kJ/(K}\cdot\text{mol)} \times 298\text{ K} = -7.432\text{ kJ}$.
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