Chapter 17, Problem 54E

Two crystalline forms of white phosphorus are known. Both forms contain P₄ molecules, but the molecules are packed together in different ways. The α form is always obtained when the liquid freezes. However, below −76.9°C, the α form spontaneously converts to the β form:

${\text{P}}_4\left(s,\alpha \right)\to {\text{P}}_4(s\text{,}\beta )$

a. Predict the signs of ∆H and ∆S for this process.

b. Predict which form of phosphorus has the more ordered crystalline structure (has the smaller positional probability).