The entropy of water at atmospheric pressure and $100^{\circ} \mathrm{C}$ is $0.31$ $\mathrm{cal} / \mathrm{g} \cdot \mathrm{deg}$, and the entropy of steam at the same temperature and pressure is $1.76 \mathrm{cal} / \mathrm{g} \cdot \mathrm{deg}$.

What is the heat of vaporization at this temperature?
Heat of vaporization is

$$
L=T \Delta S=540 \mathrm{cal} / \mathrm{g} .
$$