Past exam of the year 2 of the earth sciences (geology) course of the University of Oxford / 2024 / Paper 3 / 9 / d / Solution

For fugacity coefficient $\varphi =0.75$, use $f=\varphi P=3375\mathrm{bar}$ for the water activity. The solid pressure correction still uses the actual pressure $4500\mathrm{bar}$. ThusLowering the water chemical potential favours the product side, which lowers the equilibrium temperature relative to part (c) under the stated constant-property model.