Question

For a sample of perfect gas when its pressure is changed isothermally from $p_i$ to $p_f$, the entropy change is given by

• A. $\Delta S = nR \, ln \bigg( \frac{P_f}{p_i}\bigg)$
• B. $\Delta S = nR \, ln \bigg( \frac{p_i}{p_f}\bigg)$
• C. $\Delta S = nRT\, ln \bigg( \frac{p_f}{p_i}\bigg)$
• D. $\Delta S = RT \, ln \bigg( \frac{p_i}{p_f}\bigg)$

Answer 1

Answer: (B)

$\Delta S = nR \, ln \bigg( \frac{p_i}{p_f}\bigg)$

Answer 2

$\Delta S = nR \, ln \frac{P_1}{P_f}$