Standard Molar Entropy
The absolute entropy of one mole of a substance in its standard state at 298 K.
Formula / equation
ΔS° = ΣS°(products) − ΣS°(reactants)
Unit
J/(mol·K)
In depth
Because the third law fixes a zero, standard entropies are tabulated as absolute values and are always positive for any substance above 0 K. They increase with molecular complexity, molar mass and disorder of the phase, and combine additively to give the entropy change of any reaction.
Examples in the real world
Diamond has a very low 2.4 J/(mol·K) thanks to its rigid lattice; gaseous CO₂ has 214.