U2-2-3 - Free Energy

Question 1

What sign (+ or −) will ∆G° have for a spontaneous reaction?

Answer 1

Negative (−)

Question 2

What must be done before we can plug ∆S° into the equation

∆G° = ∆H° − T∆S°?

Answer 2

∆S° must be divided by 1000 (to convert to kJ K^-1 mol^-1)

Question 3

No temperature is given in the question but we must use the equation ∆G° = ∆H° − T∆S°.

What temperature should be used?

Answer 3

298 K

(° implies standard conditions)

Question 4

How do we use the equation ∆G° = ∆H° − T∆S° to work out the T at which the reaction becomes feasible?

Answer 4

Let ∆G° = 0

(then T = ∆H° / ∆S°)