A technique used to overcome the unfavorable thermodynamics of one reaction is to “couple” that reaction to another process that is thermodynamically favored. For instance, the dehydrogenation of cyclohexane to form benzene and hydrogen gas is not spontaneous.

Show that, if another molecule such as ethene is present to act as a hydrogen acceptor (that is, the ethene reacts with the hydrogen produced to form ethane), then the overall process is spontaneous.