Chemistry · Chapter 16

Spontaneous or Not?

Pick an everyday change, set the temperature, and call it before the answer shows. A spontaneous change runs downhill in free energy. The hill in front of it decides how long the trip takes.

The free energy landscapeball sits on the reactant side

The numbersΔG = ΔH − TΔS

−0.5kJ  ΔG spontaneous
ΔH° 
ΔS° 
T 
TΔS° 
crossover T 

Entropy is listed in J/K, so it is divided by 1000 before the subtraction. Mixing joules with kilojoules here is the most common mistake in the whole chapter.

Pick a change

Temperature298 K

Your call0 right of 0

Start here
Choose a change, then call it
Set the temperature first. Then say whether the change runs on its own. The landscape and the numbers appear either way.