Gibbs free energy

Question 1

What is the equation to calculate ΔG?

Answer 1

ΔG = ΔH - TΔS

Question 2

What do you need to remember to do to TΔS?

Answer 2

divide by 1000

Question 3

What is ΔS?

Answer 3

entropy, a measure of disorder

Question 4

List the 3 states and their corresponding entropies

Answer 4

solid - liquid - gas
low entropy —-> high entropy

Question 5

At 0K, the entropy of all substances is…

Answer 5

zero

Question 6

On an entropy graph, what are the straight vertical lines?

Answer 6

melting/boiling points, boiling point is bigger

Question 7

In terms of entropy, hotter solids have….

Answer 7

greater entropy as particles vibrate more

Question 8

At the melting point, there is a large increase in entropy because….

Answer 8

vibrating solid particles turn into randomly moving liquid particles

Question 9

At the boiling point, there is a VERY large increase in entropy because….

Answer 9

randomly moving liquid particles turn into randomly moving chaotic gas particles

Question 10

ΔS boiling is

Answer 10

GREATER than ΔS melting

Question 11

How do you calculate entropy?

Answer 11

ΔS = ΣΔS products - ΣΔS reactants

Question 12

What happens to entropy when ΔS is positive?

Answer 12

increase in disorder, increase in entropy

Question 13

What happens to entropy when ΔS is negative?

Answer 13

decrease in disorder, decrease in entropy

Question 14

What impact does the moles of gas have on ΔS?

Answer 14

if there are equal moles of gas on both sides of the equation, then ΔS is small

Question 15

When is a reaction feasible/spontaneous?

Answer 15

when ΔG is zero or negative, and ΔS is positive, ΔH is negative

Question 16

When is a reaction infeasible?

Answer 16

when ΔG is positive, ΔS is negative, ΔH is positive

Question 17

What happens when ΔH and ΔS are both negative?

Answer 17

only feasible below certain temps

Question 18

What happens when ΔH and ΔS are both negative?

Answer 18

only feasible above certain temps

Question 19

How do you calculate the temperature at which a reaction becomes feasible?

Answer 19

T = (ΔH) / (ΔS/1000)

Question 20

Describe how you would lay out the graph for temperature and ΔG?

Answer 20

ΔG = -ΔS x T + ΔH
y = m x + C
x axis = T
y axis = ΔG
gradient = -ΔS
y-intercept = ΔH