Q56 / 180 · COMEDK 2025 (10 May Shift 2) · Chemistry
The Enthalpy of combustion of 1.0 mole of a reactive metal X at $27^{\circ} \mathrm{C}$ and 1.0 bar pressure to form a solid oxide (XO) is $-601.83 \mathrm{~kJ} / \mathrm{mol}$. The Internal energy change for this reaction is ______ kJ .
$\left(\mathrm{R}=8.314 \mathrm{J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}\right)$
- A$-614.30$
- B$701.33$
- C$754.58$
- Correct answerD$-600.58$
Solution
Reaction: $X_{(s)} + \dfrac{1}{2}O_{2(g)} \rightarrow XO_{(s)}$
$\Delta n_g = 0 - \dfrac{1}{2} = -0.5$ mol
$\Delta U = \Delta H - \Delta n_g RT$
$\Delta U = -601.83 - (-0.5 \times 8.314 \times 10^{-3} \times 300)$
$\Delta U = -601.83 + 1.247 = -600.58$ kJ
$\Delta n_g = 0 - \dfrac{1}{2} = -0.5$ mol
$\Delta U = \Delta H - \Delta n_g RT$
$\Delta U = -601.83 - (-0.5 \times 8.314 \times 10^{-3} \times 300)$
$\Delta U = -601.83 + 1.247 = -600.58$ kJ
Hence, the correct answer is option: 'D'.