For which of the reactions listed below will Gibbs free energy always be negative?
A. An exothermic reaction that decreases in entropy
B. An endothermic reaction that decreases in entropy
C. An endothermic reaction that increases in entropy
D. An exothermic reaction that increases in entropy

Solid tin exists in two forms: white and gray. for the transformation sn(s, white) → sn(s, gray) the enthalpy change is -2.1 kj/mol and the entropy change is -7.4 j/(mol*k). a. calculate the gibbs free energy change for the conversion of 1.00 mol white tin to gray tin at -30℃. b. will white tin convert spontaneously to gray tin at -30℃? c. at what temperature are white and gray tin thermodynamically equivalent at a pressure of 1 atm?