Free-energy change

Question 1

What is the symbol for free-energy change?

Answer 1

ΔG

Question 2

What is free-energy change a measure of?

Answer 2

A measure used to predict whether a reaction is feasible

Question 3

When is a reaction feasible?

Answer 3

It will carry on once started without any energy being supplied to it.
If ΔG is negative or equal to zero

Question 4

What is the equation to calculate free-energy change?

Answer 4

ΔG = ΔH - TΔS

Question 5

What are the units for the parts of the free energy change equation?

Answer 5

ΔG = Jmol-1
ΔH = Jmol-1
T = K
ΔS = JK-1 mol-1

Question 6

When will a reaction be feasible at any temperature?

Answer 6

If a reaction is exothermic and has a positive entropy change

Question 7

When is a reaction not feasible at any temperature?

Answer 7

If a reaction is endothermic and has a negative entropy change

Question 8

What happens to the feasibility of the reaction if ΔH is positive and ΔS is positive?

Answer 8

The reaction will only be feasible above a certain temperature

Question 9

What happens to the feasibility of the reaction if ΔH is negative and ΔS is negative?

Answer 9

The reaction will only be feasible below a certain temperature

Question 10

How can you calculate enthalpy change and entropy change from a graph?

Answer 10

Rearrange the free energy equation to get it into the same form as the equation of a straight line
ΔG = (-ΔS x T) + ΔH
y = ( m x X ) + c