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JEE Main levelSingle correct optionDifficulty 2 of 3td124

A gas expands irreversibly from $2.0 L$ to $12.0 L$ against a constant external pressure of $2.0 atm$ . Taking $1 L atm = 101.3 J$ , the work $w$ (IUPAC convention, work done on the system) is

A $+ 2026 J$
B $- 2026 J$
C $- 2431 J$
D $- 203 J$

Answer: B

w = - P_{e x t} Δ V = - 2.0 \times (12.0 - 2.0) = - 20 L atm = - 20 \times 101.3 = - 2026 J

. The sign is negative because the gas does work on the surroundings; using

V_{2}

alone gives

- 2431 J

and a factor-of-10 slip in

Δ V

gives

- 203 J

.

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