Question
An ideal gas expands from initial volume 5\ dm ^3 to 15\ dm ^3 against a constant external pressure of 2 atm. What is the work done by the gas ?
MHT CET
Chemistry
Thermodynamics (C)
2026
MHT CET 2026 (19 April Shift 1)
MHT CET Chemistry Question (2026) — Solution
Options
- A. -1202.6 J
- B. -2026.4 J
- C. -1101.32 J
- D. -1013.2 J
Answer
B. -2026.4 J
Step-by-step solution
The work done by a gas during expansion against a constant external pressure is given by the formula: W = -P_ ext V Given: P_ ext = 2\ atm V_i = 5\ dm ^3 = 5\ L V_f = 15\ dm ^3 = 15\ L Change in volume: V = V_f - V_i = 15 - 5 = 10\ L Substituting the values into the formula: W = -2\ atm 10\ L = -20\ L \ atm To convert the work done into Joules, use the conversion factor 1\ L \ atm = 101.32\ J : W = -20 101.32\ J = -2026.4\ J Answer: -2026.4 J
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