Q30 / 180 · COMEDK 2024 (Evening Shift) · Chemistry

The Enthalpy of combustion of $\mathrm{C}_6 \mathrm{H}_5 \mathrm{COOH}(\mathrm{s})$ at $25^{\circ} \mathrm{c}$ and 1.0 atm pressure is $-2546 \mathrm{~kJ} / \mathrm{mol}$. What is the Internal energy change for this reaction?

  • A
    $-2552.2 \mathrm{~kJ}$
  • Correct answer
    B
    $-2544.8 \mathrm{~kJ}$
  • C
    $-2560.3 \mathrm{~kJ}$
  • D
    $-2539.8 \mathrm{~kJ}$

Solution

$C_6H_5COOH(s) + \dfrac{15}{2}O_2(g) \rightarrow 7CO_2(g) + 3H_2O(l)$

$\Delta n_g = 7 - \dfrac{15}{2} = -0.5$ mol

$\Delta U = \Delta H - \Delta n_g RT = -2546 - (-0.5 \times 8.314 \times 10^{-3} \times 298)$

$\Delta U = -2546 + 1.2388 = -2544.8$ kJ

Hence, the correct answer is option: 'B'.

Relevant Questions