1. 15-5 Reaction Spontenaity
A spontaneous reaction is one that proceeds without outside actions/intervention, on its own, once it has started.
The 2 factors that determine spontaneity are entropy and enthalpy.
Entropy is a measure of disorder.
The 2nd law of thermodynamics states that entropy of the universe is always increasing.

2. Entropy
There are 6 ways you can predict an increase/decrease of Entropy . (S)
Entropy increases with state changes from
solidliquidgasplasma
2. The dissolving of a gas in a solution decreases S.
More gaseous substances indicates an increase in S.
Entropy increases when a solid or liquid dissolves in a solvent.
Entropy increases with increase in temperature.
More parts indicates higher entropy than fewer parts of a whole.

3. Gibb’s Free Energy
Gibb’s free energy (or free energy) is the energy available to do work.
Our main equation for calculating free energy is …
ΔG system = ΔH system – TkΔS system (Temp must be K)
Example: A system has …
temperature = 25.0oC
ΔS= j/K
ΔH =145 kJ
What is the value for Gibb’s Free energy?
Is this reaction spontaneous and why?

4. Solution
ΔG system = ΔH system – TkΔS system