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; densityM1.88 g/cm). P4(s, a) P4(s, B) Indicate which of the following statements are true or false, with regard to the above process. true true false true true false The a phase has the less ordered crystalline structure. At -76.9°C, AG for this process is less than zero. Above -76.9°C, the sign of AG for this process is negative. At -76.9°C, the two solid phases cannot coexist. The sign of As for this process is negative. The sign of AH for this process is positive. cf Section 10.7 "Free Energy" pp 368-71 in Zumdahl Chemical Principles 8th ed.

Answer 1

1. The statment - The $\alpha$ phase has less ordered crystalline strucure. is TRUE

2. The statment - At -79.9C, the deltaG for this process is less than zero. is TRUE

3. The statment - Above -79.9C, the sign of deltaG for this process is negative. is FALSE

4. The statment - At -79.9C, the two solid phase cannot coexist. is TRUE

5. The statment - The sign of deltaS for this process is negative. is TRUE

6. The statment - The sign of deltaH for this process is positive. is FALSE