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MHT CET202523 Apr 2025Evening ShiftChemistryThermodynamics (C)Actual

Calculate work done if 1 mole of an ideal gas expands isothermally from 2 dm ^3 to 2.8 dm ^3 against constant external pressure 1 atm

Options

  1. A-40 52 ~J
  2. B-81.04 ~J
  3. C-121.56 ~J
  4. D-60 78 ~J

Correct answer

B. -81.04 ~J

Step-by-step solution

The work done by an ideal gas expanding isothermally against constant external pressure is given by W = -P_ ext V . With initial volume V₁ = 2 dm ^3 , final volume V₂ = 2.8 dm ^3 , and external pressure P_ ext = 1 atm , the volume change is V = V₂ - V₁ = 0.8 dm ^3 . Substituting these values yields W = -(1 atm )(0.8 dm ^3) = -0.8 atm dm ^3 . Converting to joules using 1 dm ^3 = 1 L and 1 L atm = 101.325 J gives W = -0.8 101.325 J = -81.06 J . This result corresponds most closely with option B ( -81.04 J ), with the

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