Entropy and Gibbs Free Energy.ppt

to enhance the knowledge about phase transformation, and clear the basics of thermodynamics.

1. Entropy and Gibbs Free
Energy
Chemistry
Mr. Hamza Suharwardi

2. Spontaneous Process
A process that occurs without outside
intervention/involvement.
Spontaneous processes can be fast or
slow!

3. What Factors Determine the
Spontaneity of a Reaction?
Entropy
Enthalpy
What ties the two together is:
Gibbs Free Energy.

4. Entropy
Symbol S
A measure of molecular randomness or
disorder.

5. Disorder
Chemical processes
spontaneously go to a direction
of increased entropy.
Why?
Probability

6. Probability of Disorder
Is there a higher probability your room
will be messy or neat as time goes on?

7. System
the part of the universe under investigation.

8. Entropy of the System
Is greater in:
Gases than solids.
Larger volumes of gases than smaller volumes.
Larger number of gas molecules than smaller
number of gas molecules.

9. Example:
Which has more entropy in its system?
H
2O (s) orH
2O (g)

10. Enthalpy (Heat of Reaction)
Enthalpy (H) isthe sum of the internal
energyand pressure times volume .
We cannot measure the enthalpy of a
system, but we can look at changes in
enthalpy. H = E + P V.
Spontaneity is favored when the process is
exothermic(DH<0).
Anexothermicprocessreleasesheat,
causingthetemperatureoftheimmediate
surroundingstorise.Anendothermic
processabsorbsheatandcoolsthe
surroundings.”

15. Example of a spontaneous exothermic
reaction:
2SO
2(g)+ O
2(g)2SO
3(g) + heat
DH<0

16. So…… :
When
DH <0 and DS
system>0
(exothermic) (Greater Disorder)
the reaction would be spontaneous.

17. Are all spontaneous reactions
exothermic and with a greater
system disorder?
Answer: No.

18. What about exothermic and less
disorder? Use Gibbs Free Energy
Gibbs Free Energy can be used to predict
the spontaneity and it ties together the
DH and the DS, the two driving forces of
reactions.
DG= DH-TDS
(all quantities refer to the system)

19. Gibbs Free Energy
Energy that can be converted to work.
DG<0 for spontaneous processes.
DG=0 at equilibrium.

20. Thanks!
Any questions?
You can find me at
●@hamzaahmed
●[email protected]