Chemistry 2720 Fall 1999 Quiz 4 Solution

The reaction has a certain entropy change . The reaction is exothermic so it will heat the contents of the adiabatic container, resulting in an entropy increase . Since the reaction is spontaneous, the second law requires that , i.e.\ that . Note that so that we cannot determine the sign of from this argument. It is tempting to conclude that is positive (due to the gaseous product), but it is in fact negative. Roughly speaking, the ionic products organize the solution in a way which more than compensates for the increased disorder due to the hydrogen gas.