Thermodynamics & Free Energy

2nd Law of Thermo

if spontaneous, delta S will increase

heat flows from hot to cold

3rd Law of Thermo

the entropy of a perfect crystalline structure at absolute zero is 0

Therefore entropy should be positive for the reaction to go

Absolute 0 is 0 Kelvin where all molecular motion stops

Spontaneity

if a reaction will occur by itself, without anything acting upon it to start it

Entropy

Delta S

must be positive

increases with more disorder

S -> l

l -> g

g -> S

Increase in temperature

how dispersed and disorders a the energy in a system is

Enthalpy

Typically spontaneous when negative (exothermic)

typically spontaneous when positive

Typically nonspontaneous when positive (endothermic)

delta H

Free Energy

Gibbs Free Energy

The amount of energy available to do work

Delta G

Typically spontaneous when negative

delta G is 0 at equillibrium

delta G standard= delta H standard - (Temperature)(delta S standard)

entropy and enthalpy alone does not indicate spontaniety

Calculated By

Delta S, Delta H, and Temp given

Finding Delta S and Delta H through formation rxns

Hess's Law (coupled reactions)