JEE Main · 2023 · 30 Jan 2023 · Shift 1 · Chemical Thermodynamics

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When 2 litre of ideal gas expands isothermally into vacuum to a total volume of 6 litre, the change in internal energy is ______ J. (Nearest integer)

Answer: 0

Solution

The internal energy of an ideal gas depends only on its temperature, because there are no intermolecular forces whose potential energy could vary with volume. The change described is isothermal, so the temperature is unchanged and

Δ T = 0

. Expansion into a vacuum is a free expansion against zero external pressure, in which no work is done, and with the temperature held fixed the internal energy cannot change. The change in internal energy of the gas is

0 J

JEE Main · 2023 · 30 Jan 2023 · Shift 1 · Integer answer

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