Entropy

Question 1

What is entropy

Answer 1

Measure of dispersal in a system
Eg. No of ways particles can be arranged
Eg. No of ways energy is shared between the particles

Question 2

What does high disorder mean in terms of entropy

Answer 2

Higher entropy

So a large positive value

Question 3

What state has the lowest entropy

Answer 3

Solids

Question 4

Why do different states have different entropy

Answer 4

Solids = vibrate about a fixed position = Low disorder = low entropy 
Gas = vibrate and move around the volume. In random arrangements ans random movements = high disorder = high entropy

Question 5

How does the number of particles affect entropy

Answer 5

The more particles there are
The more ways they can be arranged
The more ways energy can be arranged
Increases entropy

Question 6

What happens to entropy in this reaction:

N2O4 -> 2No2

Answer 6

The number of moles increases on the products
So disorder increases
Increases entropy

Question 7

Why do substances try to increase their entropy

Answer 7

More disorder leads to them being more energetically stable

Question 8

Why are some reactions feesible

Answer 8

The product of the reaction has a higher entropy

The increase in entropy increases the change in enthalpy

Question 9

What happens when a substance reaches its maximum entropy state

Answer 9

It’s thermodynamically stable

Won’t react any further without some energy input

Question 10

What is the equation for entropy change of a reaction

Answer 10

🔺s = s(p) - s(r)

Question 11

What values of entropy are mor likely to be feasible

Answer 11

Large positive 🔺s

Question 12

What are the 3 factors that a reaction depends on to happen

Answer 12

🔺s (entropy)
🔺H (enthalpy)
T (temp)

Question 13

What is the symbole for free energy

Answer 13

🔺G

Question 14

What is the equation for free energy

Answer 14

🔺G = 🔺H - (Tx🔺S)

Question 15

What are the units for 🔺H

Answer 15

Jmol-1

Question 16

What is the units for🔺s

Answer 16

kJmol-1

Question 17

If 🔺G is +ve what does that mean in terms of feasibility

Answer 17

It’s not feasible

Question 18

What does it mean in terms of feasibility if 🔺G = 0

Answer 18

The reaction is on,y just feasible

Question 19

What is the equation for the temperature when the reaction is ONLY JUST feasible (🔺G = 0)

Answer 19

T = 🔺H/🔺S

Question 20

Using the equation when is the reaction feasible

Answer 20

🔺H = -ve
🔺S = +ve 
🔺G = -ve

Question 21

Using the equation when is the reaction not feasible

Answer 21

🔺H = +ve 
🔺s = -ve 
🔺G = +ve

Question 22

Why, even if the 🔺G is -ve, might the reaction not happen

Answer 22

Might have a really high activation energy

Have a really slow rate = looks like nothing is happening