Q26 / 150 · MHT CET 2023 (13 May Shift 1) · Chemistry

One mole of an ideal gas performs $900 \mathrm{~J}$ of work on surrounding. If internal energy increases by $625 \mathrm{~J}$, find the value of $\Delta \mathrm{H}$.

  • A
    $-275 \mathrm{~J}$
  • B
    $200 \mathrm{~J}$
  • C
    $-150 \mathrm{~J}$
  • Correct answer
    D
    $1525 \mathrm{~J}$

Solution

$\begin{array}{ll} & \mathrm{W}=-900 \mathrm{~J}, \Delta \mathrm{U}=+625 \mathrm{~J} \\ & \text { Assuming constant pressure, } \\ & \Delta \mathrm{H}=\Delta \mathrm{U}+\mathrm{P}_{\mathrm{ext}} \Delta \mathrm{V} \\ \therefore \quad & \Delta \mathrm{H}=\Delta \mathrm{U}-\mathrm{W} \\ \therefore \quad & \Delta \mathrm{H}=+625-(-900)=1525 \mathrm{~J}\end{array}$

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

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