The vapour pressures of water and ice at are 0.28 and 0.26 Pa, respectively. What is the free energy — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

The initial and final states are respective equilibrium boundaries where $\Delta G_{\text{phase}} = 0$. The overall $\Delta G$ equates to the reversible isothermal expansion of the vapor from 0.28 Pa to 0.26 Pa. $\Delta G = nRT \ln(P_2/P_1) = 1 \times R \times 263 \times \ln(0.26/0.28) = R \times 263 \times \ln\left(\frac{13}{14}\right)$.