What are some of the observable changes that are evidence that a chemical reaction has taken place?

in the analysis of systems that involve fluid flow, we frequently encounter the combination of properties u and pv.

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.