Free energy

Question 1

What is the formula for free energy change?

Answer 1

ΔG = ΔH - TΔS

Question 2

What are the units for free energy change?

Answer 2

kJ mol⁻¹

Question 3

What are the units for ΔH?

Answer 3

kJ mol⁻¹

Question 4

What are the units for ΔS?

Answer 4

J K⁻¹ mol⁻¹

Question 5

What are the units of T?

Answer 5

Kelvin

Question 6

What do you need to do to ΔS so the equation is consistent?

Answer 6

Need to divide by 1000

Question 7

What is the condition for ΔG to be feasible?

Answer 7

It must be negative

Question 8

Why might a feasible process not actually appear to occur?

Answer 8

If the activation energy is very large, then the rate of the reaction my be too slow to be perceived

Question 9

What’s the importance of temperature on a reaction?

Answer 9

Above a certain temperature, a reaction will be feasible

Question 10

How do you calculate the temperature when a reaction becomes feasible?

Answer 10

ΔH / ΔS (when G = 0)

Question 11

Will a reaction be feasible if ΔH is negative and ΔS is positive?

Answer 11

Always, regardless of T

Question 12

Will a reaction be feasible is both ΔH and ΔS are negative?

Answer 12

Only when T is low enough so that [TΔS] < [ΔH] (freezing, needs to decrease temp.)

Question 13

Will a reaction be feasible when both ΔH and ΔS are positive?

Answer 13

Only when T is high enough to make [TΔS] > [ΔH] (boiling, needs to increase temp.)

Question 14

Will a reaction be feasible if ΔH is positive and ΔS is negative?

Answer 14

Never, regardless of T