Question

The entropy change in the isothermal reversible expansion of $2$ moles of an ideal gas from $10$ to $100\, L$ at $300 \,K$ is

• A. $42.3 \,JK ^{-1}$
• B. $35.8 \,JK^{ -1}$
• C. $38.3 \,JK^{-1}$
• D. $32.3\, JK^{-1}$

Answer 1

Answer: (C)

For isothermal reversible expansion
$\Delta S=n R \ln \frac{V_{2}}{V_{1}}$ or $ 2.303 n R \log \frac{V_{2}}{V_{1}}$
Given, $ n =2, V_{2}=100, V_{1}=10 $
$=2.303 \times 2 \times 8.314 \times \log \frac{100}{10} $
$=2.303 \times 2 \times 8.314 \times 1 $
$=38.3 \,J / K $