Question

Two moles of an ideal gas are allowed to expand reversibly and isothermally at $300\, K$ from a pressure of $1\, atm$ to a pressure of $0.1\, atm$. The change in Gibbs free energy is

• A. -11.488 J
• B. +11.488 J
• C. -11.488 kJ
• D. zero

Answer 1

Answer: (C)

Use the following equation,
$\Delta G=2303\, n R T \log \left(\frac{p_{2}}{p_{1}}\right)$
$\therefore \Delta G=2.303 \times 2 \times\left(8.314 J K^{-1} mol ^{-1}\right)$
$\times(300\, K) \times \log \left(\frac{0.1 atm }{1 atm }\right)$
$=-11488\, J =-11.488\, kJ$