Question

Spontaneity of Solid Phase Change Two crystalline phases of white phosphorus are known. Both contain P4 molecules, but the molecules are packed together in different ways. The a phase of the solid (P4; density=1.82 g/cm2) is always obtained when molten phosphorus crystallizes below the melting point (44.1 °C). However, when cooled below -76.9 °C, the a phase spontaneously converts to the B phase (P4; density=1.88 g/cm). P4(s, a) P4(s, B) Indicate which of the following statements are true or false, with regard to the above process. The a phase has the more ordered crystalline structure. At -76.9°C, both solid phases can coexist indefinitely. Above -76.9°C, the sign of AG for this process is positive. The sign of As for this process is negative. At -76.9°C, AG for this process is less than zero. The sign of AH for this process is negative.

Answer 1

Your answer is

phase has the more ordered crystalline structure

As below melting point it has density 1.82 g/cm^{​​​​​3} and cooled below -76.9 °c it has density 1.88 g/cm​​​^{​​​​​3} this indicates that the $\beta$ phase has perfectly ordered crystalline structure