Enthalpy and Entropy

Question 1

Define entropy

Answer 1

A measure of the dispersal of energy in a system which is greater when the system is more disordered.

Question 2

What is the symbol of entropy

Answer 2

S

Question 3

Which is more disordered, solid or gas

Answer 3

gas

Question 4

What is the standard unit of entropy

Answer 4

JK-1mol-1

Question 5

How does temperature affect entropy

Answer 5

Greater temperature means particles have more energy and move more. So arrangement of particles become more random = higher entropy.

Question 6

When a solid ionic lattice is dissolved in solution what happens to entropy

Answer 6

Entropy increases because ions are more disordered

Question 7

How does change in number of gas molecules in a reaction affect entropy

Answer 7

Increase in gas molecules = increase in entropy
Decrease in gas molecules= decrease in entropy

Question 8

Write the equation used to calculate entropy change

Answer 8

S = P - R
(products) - (reactants)

Question 9

Write the Gibbs free energy equation and state what each symbol means

Answer 9

ΔG=ΔH–TΔS
(change in Gibbs free energy) = (enthalpy change)- (temperature)(entropy change)

Question 10

For a reaction to be feasible ΔG must be positive or negative

Answer 10

negative

Question 11

What are the limitations of predictions of feasibility made by using ΔG

Answer 11

Reaction may have high activation energy
Rate of reaction may be very slow