Chapter 19 Notes

Chapter 19 NotesChemical Thermodynamics-Entropy and The Laws of Thermodynamics

Spontaneous ReactionsCH4(g) + 2 O2(g) CO2(g) + 2 H2O(l)H2O(s) H2O(l) at 25oC

Factors Affecting Spontaneity:1. Energy Factor: at 25oC, 1 atm, exothermic reactions are ordinarily spontaneous (H 0H2O(l) H2O(g)S > 0Fe2O3(s) + 3 H2(g) 2 Fe(s) + 3 H2O(g) S > 0

All of these reactions are endothermic (H > 0). They become spontaneous at high temperatures.Ammonium dichromate volcano

Second Law of ThermodynamicsThe entropy of the universe increases in any spontaneous process.

Reversible processes have a zero entropy change for the universe but are not real processes, just idealized thought experiments.First Law of ThermodynamicsThe energy of the universe is conserved

Third Law of ThermodynamicsThe entropy of a pure crystalline substance at 0 K is zero.

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