1
Chapter 20
Thermodynamics:
Entropy, Free Energy and the
Direction of Chemical Reactions
“Take Home Lessons”
Thermodynamics: Simple Elegant Relations that
Teach Us the Directions of Reactions and
Maximum Extractable Work
⇒
Entropy makes the world go round
⇒
Entropy is simply the number of different
possible permutations/probability to have certain
arrangement of atoms AND
energy
⇒
Entropy also referred to as disorder
⇒
Entropy
≥
0 (always increases iff change)
Thermodynamics:
Entropy, Free Energy, and the Direction of Chemical Reactions
20.1
The Second Law of Thermodynamics:
Predicting Spontaneous
Change
→
energy/heat needed …. Probability of gaining net energy to
drive reaction related to entropy (Second Law of Thermodynamics
Δ
S>0)
20.2
Calculating the Change in Entropy of a Reaction (Third Law of
Thermodynamics S=0 at T=0
→
absolute determination of entropy)
20.3
Entropy, Free Energy, and Work
20.4
Free Energy, Equilibrium, and Reaction Direction
{
“Suggested” Problems:
Chapter 20:
2, 5, 10, 12,16,18, 20, 22, 24, 26, 28,
31, 33, 37, 46, 56, 58, 62, 64, 65, 66,
68, 72, 78, 80, 83, 87, 96,
99,104,106,110
Be sure to be understand free energies and connection to entropy.
Develop facility to use free energies, entropy, enthalpies to predict reaction
direction from starting conditions and maximum work/energy that can
extracted