[Closed book.]

1a. In the "reaction" C₃H₈ (liq) --> C₃H₈(aq) S^o is (negative, zero, positive). (4 pts)

(Entropy change of the system is negative because aqueous solvent molecules become structurally "ordered" around each solvated propane molecule.)

1b. In a reaction such as C₃H₈(aq) + C₃H₈(aq) --> (C₃H₈)₂ (aq), G^o₂₉₈ is expected to be (negative, zero, positive). (4 pts)

(The number of ordered solvent water molecules is greater around isolated non-polar solvents and so the expectation is that the change occurs spontaneously as written.)

2a. The Gibbs free energy to convert white phosphorus (P₄) into red phosphorus (also P₄) is +13.82 kJ/mole at 25^o C. White phosphorus (will, will not) convert spontaneously into red phosphorus at 25^o C. (4 pts)

(A positive change in the Gibbs free energy for a process indicates that the process is not spontaneous; it will not proceed in the direction indicated.)

2b. Red phosphorus is a more ordered structure than white phosphorus. An (increase, decrease) in temperature will make the conversion of white phosphorus into red phosphorus more spontaneous. (4 pts)

(G(T)= H-T S; for ~constant H and S, G(T')-G(T)=-(T'-T)S; for the product being more ordered than the reactant (white phosphorus), S is negative. A decrease in temperature makes (T'-T) negative and the -(T'-T)S negative, favoring formation of the product (red phosphorus).)

2c. The density (specific gravity) of red phosphorus is 2.34 g/cm³ and that of white phosphorus is 1.82 g/cm³. What effect will an increased in pressure have on the transition between the two phases (assuming the densities of each phase are approximately constant)? (4 pts)

[corrected] (G(P',red)-G(P,red)=V(red)P; G(P',white)-G(P, white)=V(white)P; subtract to get G(P')-G(P)=V(P'-P); Since P'-P is positive, a negative V favors the transition (white-->red). A negative V corresponds to the opposite direction of changes in density. (A higher density for red phosphorus favors its production at increased pressure.) The red phosphorus is favored.