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Entropy of mixing in condensed phases
1/5 When a pure substance of molecule A mixes with a pure substance of molecule B, the entropy of the mixture exceeds the sum of the entropies of the two pure substances.
The excess is called the entropy of mixing.
Entropy of mixing in condensed phases
1/5 When a pure substance of molecule A mixes with a pure substance of molecule B, the entropy of the mixture exceeds the sum of the entropies of the two pure substances.
The excess is called the entropy of mixing.
2/5 Molecules A and B can have different volumes. A molecule can jiggle into many shapes. For example, A can be a macromolecule, and B a solvent molecule.
Mixing is taken to change neither the volume of each molecule, not the number of shapes that each molecule can jiggle into.
Mixing is taken to change neither the volume of each molecule, not the number of shapes that each molecule can jiggle into.
3/5 What does mixing do? It lets each molecule explore a larger volume!
Each molecule A explores volume (n_A)(V_A) in the pure substance, but explores volume (n_A)(V_A) + (n_B)(V_B) in the mixture. Similarly for B.
Mixing increases the number of configurations by a factor:
Each molecule A explores volume (n_A)(V_A) in the pure substance, but explores volume (n_A)(V_A) + (n_B)(V_B) in the mixture. Similarly for B.
Mixing increases the number of configurations by a factor:
