Question
Calculate the change in internal energy if an ideal gas expands from 0.5\ dm ^3 to 3.5\ dm ^3 at constant pressure 2 bar by absorbing 1800 J heat energy.
MHT CET
Chemistry
Thermodynamics (C)
2026
MHT CET 2026 (20 April Shift 2)
MHT CET Chemistry Question (2026) — Solution
Options
- A. 1200 J.
- B. -1200 J.
- C. 2400 J.
- D. -2400 J.
Answer
A. 1200 J.
Step-by-step solution
Given V_1 = 0.5\ dm ^3, V_2 = 3.5\ dm ^3, P = 2\ bar , and heat absorbed q = 1800\ J . Work done during expansion at constant pressure is given by W = -P(V_2 - V_1). W = -2 (3.5 - 0.5) = -6\ bar dm ^3 Since 1\ bar dm ^3 = 100\ J , we have W = -600\ J . According to the first law of thermodynamics, U = q + W. Substituting the values, U = 1800 - 600 = 1200\ J . Answer: 1200 J.
Related: Chemistry — Thermodynamics (C) · All PYQ Banks