Question
A gas expands from a volume of 1 dm^3 to 1.25 dm^3 under a pressure of 1 bar. Find the change in internal energy if 150 J of heat is supplied to the system.
MHT CET
Chemistry
Thermodynamics (C)
2026
MHT CET 2026 (13 April Shift 2)
MHT CET Chemistry Question (2026) — Solution
Options
- A. 125 J
- B. 175 J
- C. -125 J
- D. -175 J
Answer
A. 125 J
Step-by-step solution
Given V_1 = 1 dm^3 and V_2 = 1.25 dm^3. Change in volume, V = 1.25 - 1 = 0.25 dm^3 = 0.25 L. External pressure, P = 1 bar. Work done during expansion is given by W = -P V. W = -1 0.25 = -0.25 L bar. Since 1 L bar = 100 J, we have W = -0.25 100 = -25 J. Heat supplied to the system, q = 150 J. According to the first law of thermodynamics, U = q + W. U = 150 - 25 = 125 J. Answer: 125 J
Related: Chemistry — Thermodynamics (C) · All PYQ Banks