Question: What is the entropy change when 1 mole of an ideal gas expands isothermally from volume V1 to V2?

Options:

1. R ln(V2/V1)
2. R (V2 - V1)
3. R (V1/V2)
4. 0

Correct Answer: R ln(V2/V1)

Solution:

The entropy change for an isothermal expansion of an ideal gas is given by ΔS = nR ln(V2/V1). For 1 mole, it simplifies to ΔS = R ln(V2/V1).