Question

A process at constant T and P can be described as spontaneous if ?G < 0 and nonspontaneous if ?G > 0. Over what range of temperatures is the following process spontaneous? Assume that gases are at a pressure of 1 atm. (Hint: Use the data below to calculate ?H and ?S [assumed independent of temperature and equal to ?H° and ?S°, respectively] and then use the definition of ?G.)

2 SnO2(s) ? 2 SnO(s) + O2(g)

?Hf° (kJ mol-1) -580.7 -285.0 S° (J K-1 mol-1) 52.3 56.5 205.1

?H° = kJ ?S° = J K-1 The calculated value of T at which ?G° = 0 is K. Reaction is spontaneous .