Chapter 18, Problem 20PE

The heat of vaporization of ammonia is $\text{21}{\text{.7 kJ mol}}^{\text{-1}}$

and the boiling point of ammonia is $\text{-33}\text{.3 °C}$. Estimate the entropy change for the vaporization of liquid ammonia. (Hint: What algebraic sign do we expect for this entropy change?)