1. Δ U=0, Δ S_total=0 2. Δ U≠0, Δ S_total≠0 3. Δ U=0, Δ S_total≠0 4. Δ U≠0, Δ S_total=0

Topic: Second law, entropy and spontaneity· Chemical Thermodynamics

For irreversible expansion of an ideal gas under isothermal condition, the correct option is :

1. \(\Delta U=0, \Delta S_{total}=0\)

2. \(\Delta U\neq0, \Delta S_{total}\neq0\)

3. \(\Delta U=0, \Delta S_{total}\neq0\)

4. \(\Delta U\neq0, \Delta S_{total}=0\)

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Answer: 3. \(\Delta U=0, \Delta S_{total}\neq0\)

Key idea: for an ideal gas, internal energy depends only on temperature.

Isothermal means \(\Delta U=0\). An irreversible expansion is spontaneous, so the entropy of the system plus surroundings increases: \(\Delta S_{total}>0\) (it is zero only for a reversible process).

So \(\Delta U=0\) and \(\Delta S_{total}\neq0\).

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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For irreversible expansion of an ideal gas under isothermal condition, the correct option is :

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