Absolute Entropy and Entropy Changes
- The Third Law of Thermodynamics: the entropy of a perfect (ionic) crystal at 0K is zero bcus there is NO disorder (everythings is positioned perfectly)
- S values at other temps must be higher
Standard Entropy
- Standard Entropies S° (at 298K and 1 atm) (must be given)
- Pure elements have lower entropy values than larger/complex molecules
- More complex molecules have higher S° because more ways the molecules can be arranged
- S° is a state function
- Unit: j/K
= J/K x M- Total entropy of products – total entropy of reactants