3.1.8 Thermodynamics - E

Question 1

What is entropy?

Answer 1

• A measure of disorder in a system.
• In physical and chemical changes, processes move spontaneously from order to disorder. i.e entropy will increase (ΔS = +ve)

Question 2

What are the factors affecting entropy?

Answer 2

-Physical State
-Dissolving
-Number of particles

Question 3

What is the formula for entropy?

Answer 3

ΔS = Σ Sprd - Σ Srct

Question 4

ΔH cannot explain why

Answer 4

ΔH cannot explain why {{c1::endothermic reactions happen spontaneously}}

Question 5

If ΔS is +ve, is a reaction likely? What if it’s endothermic?

Answer 5

It means a reaction is likely even if it’s endothermic

Question 6

If ΔS is -ve, is a reaction likely? What if it’s exothermic?

Answer 6

It’s unlikely even if it’s exothermic

Question 7

What is the equation for Gibbs Free Energy?

Answer 7

ΔG = ΔH - TΔS

Question 8

Using ΔG, how can you tell if a reaction is feasible?

Answer 8

-If ΔG is -ve (or 0) the reaction is feasible
-If ΔG is +ve the reaction is not feasible

Question 9

4 CARDS ON GOOGLE DOCS

Question 10

What is meant by critical temperature and how do we calculate it?

Answer 10

The critical temperature is where a reaction just becomes feasible.

ΔG = 0
ΔG = ΔH - TΔS
0 = ΔH - TΔS
TΔS = ΔH
T = ΔH / ΔS

To work out the inequality, look at the signs of of dH and dS

Question 11

Recall briefly how we use calorimetry to measure energy stores in sample.

Answer 11

-Dry sample weighed + burnt in pure oxygen
-in a sealed container
-Temperature increase of the fixed volume of water used to calculate energy released