W8 Concepts of Thermodynamics

Question 1

What is Gibbs Free Energy?

Answer 1

∆G = ∆H - T ∆S

G = Gibbs Free Energy (kJ mol-1)
H = Enthalpy (kJ mol-1)
S = Entropy (J K-1 mol-1)
T = Temperature (K)

Question 2

∆G negative: Spontaneous in Forward direction only (irreversible)

∆G zero: Reaction at equilibrium, can proceed in either direction (reversible)

∆G positive: Non-spontaneous, will not proceed in the forward direction unless
coupled with an energetically favourable reaction.

Coupled reactions: Other reaction must have a larger, negative ∆G value.
Sometimes called tandem reactions.

Question 3

Free Energy of Formation (∆Gf⁰): definition

Answer 3

The free energy change which results from 1
mol of substance prepared from its elements at standard pressure (1 atm) and a
given temperature (usually 298 K). The units are kJ/mol

Question 4

Examples of thermodynamics in Biological Systems?
(for info)

Answer 4

Formation of Ala-Gly dipeptide
Hydrolysis of ATP

Question 5

The Standard Entropy Change of a Reaction (∆SӨr):

Answer 5

The difference in standard entropy
between the products and reactants of a system under standard conditions.

Question 6

What is meant by?
The Bond Dissociation Enthalpy (∆Hdiss):

Answer 6

The enthalpy change, per mol, in the gas phase, when a bond is broken of compound A –B through the reaction

Question 7

Thermochemistry

Answer 7

The study of heat changes that occur during a chemical reaction

Question 8

The Standard Enthalpy Change of Formation (∆HӨf):

Answer 8

The enthalpy change
when 1 mol of a compound is formed under standard conditions for its
constituent elements in their standard states (∆HӨf of an element = 0)

Question 9

What is the Standard Enthalpy Change of a Reaction (∆HӨr)?

Answer 9

The heat transferred by a chemical reaction or process under standard conditions