=ΔH= + / ΔS= -ΔH= + / ΔS= -
system-part of the universe under study
surroundings- the rest of the universe
state function- a quantity whose value is only determined by the initial and final states of the system
Standard conditions- Pressure of 1 bar (0.98692 atm) and solution calculations of 1 molal

Thermodynamically favored reactions are product favored. Many, but not all are exothermic.

Entropy is higher for:

• when heat is added
• gases go to liquids, and liquids go to solids
• more complex molecules
• mixtures of substances than for pure substances
• when a pure liquid or solid dissolves in a solvent
• when an ionic solid has a lower attractive force (NaF (+1, -1) has more entropy than MgO (+2, -2))

ΔS of universe= ΔS of surrounding + ΔS of system
ΔS of surrounding = q of surrounding/ T(temperature in Kelvin) = -ΔH of system/ T (temperature in Kelvin)


*in better terms, the universe favors increasing entropy, allowing reactions favoring disorder to become spontaneous
The Final State of a System can be more probable than the initial state by either or both of two ways:
1. The atoms and molecules can be more disordered
2. Energy can be dispersed over a greater number of atoms and molecules


- If energy and matter are both dispersed in a process, it is spontaneous
- if only matter is dispersed, quantative information is needed to decide whether a process is spontaneous
- if energy is not dispersed after a process occurs, then that process will never be spontaneous
ΔG=ΔH-TΔS
-spontaneous when ΔG is negative and vice versa

Gibbs free energy (G) - amount of energy that is availabe to do work
G = ΔH-TS

ΔG>0 => reactant favored/ not spontaneous/ is spontaneous in reverse
ΔG<0 => product favored/ spontaneous/ not spontaneous in reverse
ΔG=0 => Equilibrium

Third Law of Thermodynamics- there is no disorder in a perfect crystal at 0 K; S=0
ΔS= qrev/T
- all substances have positive entropy values at temperatures above 0 K
- when comparing the same or similar substances, entropies of gases are much larger than those for liquids, and entropies of liquids
are larger than those for solids.
-larger molecules have a larger entropy than smaller molecules, and molecules with more complex structures have larger entropies
than smaller molecules

∆G = ∆G° + RTlnQ
where ∆G = under nonstandard conditions
∆G° = under standard conditions
R = 8.31 J/mol K
T = temperature in K
Q = reaction quotient ([products]/[reactants])

Equilibrum
∆ G= -RTln(K)
if k>1, rxn=spontaneous
if k<1, rxn= not spontaneous
- when ΔG(rxn)<0, Q<K => reaction proceeds spontaneously to convert reactants to products until equilibrium.
- when ΔG(rxn)>0, Q>K => reaction proceeds spontaneously to convert products to reactants until equilibrium.
- when ΔG(rxn)=0, Q=K => equilibrium C:


SPONTANEITY OF REACTIONS
kdldkjf
when ΔG is -, a reaction is spontaneous; when ΔG is +, a reaction is nonspontaneous.
when the signs of ΔS and ΔH are different, the reaction will ALWAYS be either spontaneous or nonspontaneous.
when the signs of ΔS and ΔH are the same, the reaction may either be spontaneous or nonspontaneous, depending on the Kelvin temperature.
When a reaction is spontaneous, the reaction will occur.
When a reaction is not spontaneous, there is no reaction.


Gibb's Free Energy:
@ equilibrium ---
ΔGnot = -RT*Ln(K)