NEET2019Chemistry-Thermodynamics
NEET 2019 Chemistry Work done in isothermal processes MCQ Question
Type: MCQ-numerical-Medium-Class 11
Under isothermal condition, a gas at 300 K expands from 0.1 L to 0.25 L against a constant external pressure of 0.2 bar. The work done by the gas is (Given that 1 L bar = 100 J)
A
5 kJ
B
25 J
C
30 J
D
−30 J
Correct Answer
Option D
Detailed Explanation
The work done by the gas in an isothermal expansion is given by W = −P_ext × ΔV. Here, P_ext = 0.2 bar and ΔV = 0.25 L − 0.1 L = 0.15 L. Converting to joules, W = −0.2 × 0.15 × 100 = −3 J. Since the work done by the gas is positive, the correct answer is 25 J.
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