CHEM 1A03 Lecture Notes - Lecture 9: Standard Molar Entropy, Boltzmann Equation, Boltzmann Constant

• School: McMaster University
• Department: Chemistry
• Course: CHEM 1A03
• Professor: Lydia Chen

Document Summary

Reaction spontaneous in forward direction = non-spontaneous in reverse direction: e. g. Rusting: 4fe(s) + 3o2(g) 2fe2o3(s) (forward spontaneous, reverse not) Both spontaneous and non-spontaneous processes are possible. Non-spontaneous processes require system to be acted upon by external agent, e. g. energy input. Reactions naturally proceed toward side with lower energy/greater stability (either reactants or products) Spontaneity does not indicate speed of reaction; could occur rapidly (hydrogen balloon exploding) or very slowly (conversion of diamonds to graphite) Assessing whether a reaction tends to occur. Many spontaneous reactions are exothermic: e. g. Thermite: fe2o3(s) + 2al(s) 2fe(l) + al2o3(s) (heat liquefies iron) However can also be endothermic: e. g. ice packs: nh4no3(s) dissolving in water nh4+(aq) + no3-(aq) The disorder of a system; number of ways a thermodynamic system can be arranged. Boltzmann related entropy to total number of microstates a system possesses. S = klnw (s = entropy | k = boltzmann constant | w = number of microstates )