Under isothermal condition a gas expands from 0.2 dm^3 to 0.8 dm^3 against a constant pressure of 2 bar at 300 ~K . Find the work done by the gas.

Correct answer: (B) -120 ~J. W =-PdV =-2(0.8-0.2) bar-dm^2 =-2(0.6) × 10^2 ~J =-120 ~J

Q25 / 150 · MHT CET 2022 (05 Aug Shift 1) · Chemistry

Under isothermal condition a gas expands from $0.2 \mathrm{dm}^3$ to $0.8 \mathrm{dm}^3$ against a constant pressure of 2 bar at $300 \mathrm{~K}$. Find the work done by the gas.

A
$160 \mathrm{~J}$
Correct answer
B
$-120 \mathrm{~J}$
C
$-40 \mathrm{~J}$
D
$20 \mathrm{~J}$

Solution

$\begin{aligned} \mathrm{W} & =-\mathrm{PdV} \\ & =-2(0.8-0.2) \mathrm{bar}-\mathrm{dm}^2 \\ & =-2(0.6) \times 10^2 \mathrm{~J} \\ & =-120 \mathrm{~J}\end{aligned}$

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

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