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Chemistry · Glossary

What is Standard molar entropy?

Definition 2.3 University Chemistry — Year 2 · Chapter 2 — Entropy and Free Energy of Reaction

The standard molar entropy Sm∘(T)S^\circ_m(T) of a substance is the entropy of one mole of it in its standard state at temperature TT, the zero being that of the third law. Unlike ΔfH∘\Delta_f H^\circ, it is an absolute quantity, positive for every substance, elements included.

Standard molar entropy of zinc from the third-law zero. It grows with temperature as the metal stores heat, then jumps at the melting point by _ fusH/T_ fus and, much more, at the boiling point by _ vapH/T_b: a gas is far more disordered than a liquid.
Standard molar entropy of zinc from the third-law zero. It grows with temperature as the metal stores heat, then jumps at the melting point by ΔfusH/Tfus\Delta_{\text{fus}}H/T_{\text{fus}} and, much more, at the boiling point by ΔvapH/Tb\Delta_{\text{vap}}H/T_b: a gas is far more disordered than a liquid.
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