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NEETChemistryThermodynamics (C)

An ideal gas at 400 K expands isothermally from 1.0 L to 4.0 L against a constant external pressure of 2.0 bar . The heat absorbed ( q ) by the gas in this process is: (Given: 1 L bar = 100 J )

Options

  1. A-600 J
  2. B+600 J
  3. C0 J
  4. D+6 J

Correct answer

B. +600 J

Step-by-step solution

The work done by the gas against a constant external pressure is: W = -P_ ext (V_ f - V_ i ) W = -2.0 (4.0 - 1.0) = -6.0 L bar Converting to Joules: W = -6.0 100 = -600 J For an ideal gas undergoing an isothermal process, the change in internal energy is zero ( U = 0 ). According to the first law of thermodynamics: U = q + W 0 = q + (-600) q = +600 J Thus, the heat absorbed by the gas is +600 J . Answer: +600 J

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