If standard molar enthalpy change and standard molar internal energy change measured in bomb calorimeter are…

If standard molar enthalpy change and standard molar internal energy change measured in bomb calorimeter are equal, which one of the following statements is correct?
  1. $\Delta \mathrm{n}>0$, with increase in pressure
  2. $\Delta \mathrm{n}>0$, with decrease in pressure
  3. $\Delta \mathrm{n} < 0$, with increase in pressure
  4. $\Delta \mathrm{n}=0$, at constant pressure

Solution

$\Delta \mathrm{H}^{\circ}=\Delta \mathrm{U}^{\circ}$ (given) $ \begin{aligned} & \Delta \mathrm{H}^{\circ}=\Delta \mathrm{U}^{\circ}+\mathrm{P} \Delta \mathrm{V} \\ & =\Delta \mathrm{U}^{\circ}+\Delta \mathrm{nRT} \\ & =\Delta \mathrm{U}^{\circ} \end{aligned} $ $\Rightarrow \Delta \mathrm{nRT}=0$ which means $\Delta \mathrm{n}=0$ with constant pressure

Asked in: AP EAMCET 2023 (19 May Shift 1)

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