5.2.2 Enthalpy And Entropy

Question 1

What is entropy

Answer 1

Measure of the dispersal of energy in a system
Greater entropy = greater dispersal = greater disorder
Measured in JK-1mol-1
Greater entropy = greater energy is spread out per kelvin per mole

Question 2

What is positive entropy change

Answer 2

System changes to become more random, energy can spread out more

Question 3

What is standard entropy

Answer 3

Entropy of one mole of a substance under standard conditions (100kPa and 298K)
Always positive

Question 4

How to calculate entropy change

Answer 4

Sum of entropy of products - sum of entropy of reactants

Question 5

Gibbs’ equation

Answer 5

∆G = ∆H - T∆S

Question 6

How to determine feasibility of a reaction based on ∆G

Answer 6

If ∆G < O, reaction is feasible

Question 7

How does entropy vary in different physical states

Answer 7

Entropy in gas > liquid > solid

Question 8

How does entropy vary with number of gas molecules

Answer 8

More gas molecules = higher entropy value

Question 9

Limitations in the predictions for feasibility by ∆G

Answer 9

High activation energy and slow reaction rate may lead to reaction not taking place despite ∆G < 0