Answer
$−118.5\text{ kJ/kg}$
$-118.6\text{ kJ/kg}$
Work Step by Step
The saturation temperature at $300 \mathrm{~kPa}$ is $406.7 \mathrm{~K}$. Using the definition of Gibbs function and enthalpy and entropy data from Table A-5, $$
\begin{aligned}
& g_f=h_f-T s_f=(561.43 \mathrm{~kJ} / \mathrm{kg})-(406.7 \mathrm{~K})(1.6717 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K})=-118.5 \mathrm{~kJ} / \mathrm{kg} \\
& g_g=h_g-T s_g=(2724.9 \mathrm{~kJ} / \mathrm{kg})-(406.7 \mathrm{~K})(6.9917 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K})=-118.6 \mathrm{~kJ} / \mathrm{kg}
\end{aligned}
$$ which are practically same. Therefore, the criterion for phase equilibrium is satisfied.
