Entropy and Gibbs free energy

Question 1

Entropy (S)

Answer 1

a measure of the amount of disorder in a system.

Units: JK-1mol-1

Question 2

What is the formula for entropy change

Answer 2

∆S= sum of products-sum of reactants

Question 3

What does a positive/negative value mean

Answer 3

Positive=more disorder
Negative=less disorder

Question 4

Entropy and States

Gases have a much ……….. entropy compared to liquids and solids.

Solid substances have ….. entropy because their particles are highly………. Gases have very ….. entropy because their particles are moving in a ……… way

Answer 4

higher
low, ordered
high, disordered

Question 5

Entropy and Number of moles

-small number of moles———>larger number of moles
………….. in entropy

-Larger number of moles————->small number of moles
…………. in entropy

Answer 5

increase
decrease

Question 6

∆S= change in ………. can be a … or …. value

Answer 6

entropy, -ve. +ve

Question 7

A reaction is feasible when ∆G is less than or equal to zero.

Define Feasible

Answer 7

If a reaction is feasible this means that the reaction ‘can happen’ at a given temperature.

∆G ≤ 0=reaction is feasible

Question 8

What is the formula for Gibbs free energy

Answer 8

∆G = ∆H - T∆S

The balance between entropy ∆s and enthalpy ∆H determines the feasibility of a reaction

Question 9

State the units for each constant:
∆G
∆H
T
∆S

Answer 9

∆G = Gibbs Free Energy measured in kJmol-1

∆H = Enthalpy Change measured in kJmol-1

T = Temperature measured in Kelvin

∆S = Entropy Change measured in kJK-1mol-1

Question 10

Show the relationship between the Gibbs free energy formula and y=mx+c

Answer 10

y = m x + c

∆G = -∆S T + ∆H