Question

Under isothermal condition, a gas at 300 K expands from 0.1 L to 0.25 L against a constant external pressure of 2 bar. The work done by the gas is (Given that 1 L bar = 100 J)

(1)   –30 J

(2)   5 kJ

(3)   25 J

(4)   30 J

Answer 1

According to NTA official Answer key The answer will be

(A) 30J

Answer 2

Correct option (1) –30 J

Explanation:

W_irr = – P_ext ΔV

= – 2 bar × (0.25 – 0.1) L

= – 2 × 0.15 L-bar

= – 0.30 L-bar

= – 0.30 x 100 J

= – 30 J