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MHT CET202620 April 2026Evening ShiftChemistryThermodynamics (C)Actual

Which of the following processes exhibits the decrease in internal energy of a system?

Options

  1. AIsothermal expansion of an ideal gas.
  2. BIsothrmal compression of an ideal gas.
  3. CAdiabatic expansion of an ideal gas.
  4. DAdiabatic compression of an ideal gas

Correct answer

C. Adiabatic expansion of an ideal gas.

Step-by-step solution

According to the first law of thermodynamics, U = q + w . For an isothermal process, the temperature remains constant ( T = 0 ). Since the internal energy of an ideal gas depends only on temperature, U = 0 for both isothermal expansion and compression. For an adiabatic process, there is no heat exchange with the surroundings, so q = 0 . The first law becomes U = w . During adiabatic expansion, work is done by the gas on the surroundings, meaning w During adiabatic compression, work is done on the gas, meaning w > 0

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