Thermodynamics: Entropy, Free Energy, and Equilibrium
Interactive Student Tutorial

 16.5 Standard Molar Entropies and Standard Entropies
         of Reaction

Tabulated values of standard molar entropies, abbreviated S°, are available for many substances. The standard molar entropy is simply the entropy of 1 mol of a pure substance at 1 atm pressure and standard temperature (usually 25°C). The units of S° are J/(K.mol).

For the general equation, PM 1262: S° = S°(products) - S°(reactants). The standard entropy of reaction, S°, can be calculated from S° values according to

The thermite reaction is a spontaneous exothermic reaction. Watch the movie below, which shows this reaction.

 The Thermite Reaction