If a reaction is exothermic, shouldn’t that be enough to determine favorability? Actually, no!
Even if a reaction is highly exothermic, the level of order it requires may make it statistically improbable.
Concept #1: Explaining what entropy is.
Entropy (ΔS) is the tendency of a system to take its most probable form.
There are 3 common ways to make reactions more probable (increase ΔS)
Concept #2: 3 ways to increase entropy.
1. Increasing the Number of Molecules
Reactions that create extra molecules are more probable since there are more ways to arrange them.
2. Phase Transition
Transformation of solid to liquid or liquid to gas is more probable since the molecules will have a greater vibrational freedom.
3. Increasing Molecular Freedom of Motion
Converting cyclic molecules to acyclic molecules are more probable since it increases freedom of rotation.