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MHT CET202620 April 2026Evening ShiftChemistryThermodynamics (C)Actual

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.

Options

  1. A1200 J.
  2. B-1200 J.
  3. C2400 J.
  4. D-2400 J.

Correct answer

A. 1200 J.

Step-by-step solution

Given V₁ = 0.5 dm ^3 , V₂ = 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(V₂ - V₁) . 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.

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