Which of the following changes has a decrease in entropy? a. n2o4 (g) yields 2no2 (g)
b. c2h5oh (l) + 3o2 (g) yields 2co2 (g) + 3h2o (g)
c. 3o2 (g) + 2kcl (s) yields 2kclo3 (s)
d. h2o (l) yields h2o (g)

a). in this case, dh> 0 and sd> 0. if t becomes larger, the term "-tds" will become more negative. at some point, it is possible that -dts will be more negative than the dh is positive, and the reaction will become spontaneous. this is probably the correct answer, but you should look at all of the other possibilities and make sure of that.