Lecture 4

Question 1

ΔG give the…. that can be obtained from a process at…..

Answer 1

• maximum non-expansion work
• constant T and P

Question 2

How does the Gibbs free energy, G, change when the pressure and temperature change?

Answer 2

dG = Vdp - SdT

Question 3

How does Gibbs free energy change at constant temperature?

Answer 3

dG = Vdp

Question 4

Give the equation for ΔG for a solid or liquid

Answer 4

ΔG = VΔp

Question 5

Give the equation for ΔG for a perfect gas

Answer 5

ΔG = nRT ln pf/pi

Question 6

Give the equation for Gm for 1 mole of a perfect gas

Answer 6

Gm (p) = Gm° + RT ln p/p°

Question 7

Give the equation for Gm for 1 mole of a real gas pv≠nRT

Answer 7

Gm (p) = Gm° + RT ln f/p°

Question 8

Give the equation for Gm for one mole of a substance and at constant pressure

Answer 8

For one mole of a substance;
dGm = Vmdp - SmdT

At constant pressure;
dGm = -SmdT

Question 9

Give the equation for ΔG of a reaction

Answer 9

ΔrG = ∑vG (products) - ∑vG (reactants)

Question 10

Give the equation for how ΔrG changes with temperature

Answer 10

ΔrG = ΔrH - TΔrS

Question 11

What is the gradient of a graph of ΔrG against temperature?

Answer 11

m = -ΔrS