Thermodynamics (L3-1)

Question 1

Enthalpy (H) and its changes (∆H)

Answer 1

H = internal energy of system

∆H = H2 - H1

Negative in exothermic rxns

Positive in endothermic rxns

Question 2

Entropy (S)

Answer 2

A quantitative measure of the disorder or randomness of a system

Rxns tend to occur spontaneously in the direction in which S increases

Question 3

Change in Gibbs Free Energy (∆G)

Answer 3

Is the change in free energy during a rxn at any [reactants] and [products]

Predicts direction of reaction

Negative ∆G is favorable

Question 4

Standard Free Energy (ΔG°)

Answer 4

Same as ΔG, but [Reactants] and [Products] are at 1M, at 25° C

Question 5

Relationship of Keq and ΔG°

Answer 5

If Keq = 1, then ΔG° = 0

If Keq > 1, then ΔG° < 0

If Keq < 1, then ΔG° > 0

Question 6

How does energy coupling occur?

Answer 6

Occurs when the energy-requiring and energy-yielding reactions share a common intermediate (ex: ATP)

Question 7

T/F: Free energy is additive in coupled rxn sequences

Answer 7

True!

A rxn pathway may occur spontaneously (-ΔG) even if individual steps have +ΔG values

Question 8

Characteristics of ATP

Answer 8

Is often used as the common intermediate

Has 3 phosphate bonds; 2 of which are high energy bonds

Question 9

T/F: NAD+, NADP+, FAD, FMN are high energy forms

Answer 9

False! NADH, NADPH, FADH2 and FMNH2 are the reduced, high energy forms