Thermodynamics and Gibbs Free Energy

Question 1

What is the equation fo enthalpy alone?

Answer 1

deltaH = deltaU + PdeltaV
deltaH = deltaU + W
delta H = Q

Question 2

For what values of delta H is system endo/exothermic?

Answer 2

delta H > 0: system gaining or receiving heat
Endothermic

delta H > 0: system producing or losing heat
Exothermic

Question 3

Bond dissociation energy

Answer 3

bonds broken - formed

• reactants - products, but forming bonds = exothermic
• forming bonds releases energy, breaking bonds is endothermic

Question 4

Thermodynamics vs Kinetics. Classify the following:

Stability, reaction rate, activation energy, equilibrium, reaction mechanisms, spontaneity (delta G)

Answer 4

Thermo:
- stability, equilibriium, spontaneity

Kinetics:

• reaction rate
• activation energy
• reaction mech

Question 5

Equilibrium State Equation

Answer 5

delta G = -RTln Keq
> 1: products/reactants > products
< 1: products/reactants > reactants

Question 6

What is Q in regards to equilibrium?

What is the significance of Q?

Answer 6

Q is products/reactants at any point in the equation
deltaG = deltaG’ + RTlnQ
- Q < Keq: excess reactants, reaction forward to achieve equilibrium
- Q > Keq: excess products, reaction reverse to achieve eq

Q is basically where the reaction is at and what needs to happen to get back to eq

Question 7

Kinetics vs Thermodynamics: what is favored when?

Answer 7

kinetic: favored at low temp, when unstable but lower Ae
thermo: favored at higher temp, stable but high Ae

Question 8

Do catalysts/enzymes affect thermodynamics or kinetics? why?

Answer 8

kinetics: affect activation energy

don’t affect thermodynamics: stability, spontaneity, and equilibrium (products to reactants)