AP Chemistry / Topic
Applications of Thermodynamics
Unit 9 covers entropy, Gibbs free energy and spontaneity, the link between ΔG° and K, and electrochemistry: galvanic and electrolytic cells, standard cell potential, and Faraday's-law calculations.
What the exam asks
- Predict the sign of ΔS° from states of matter and gas mole counts
- Use ΔG = ΔH − TΔS to decide when a process is thermodynamically favored
- Relate ΔG° to K (favored means K > 1) and to cell potential
- Analyze galvanic cells: anode/cathode, electron flow, salt bridge, and E°cell
- Contrast electrolytic cells and compute deposited mass with Faraday's law
- Explain why favored reactions can still be slow (kinetic control)
Key formulas and rules
ΔG° = ΔH° − TΔS°; favored when ΔG° < 0
ΔH<0, ΔS>0: always favored; ΔH>0, ΔS<0: never; otherwise temperature decides
ΔG° = −RT ln K
E°cell = E°cathode − E°anode; favored when E°cell > 0; ΔG° = −nFE°
moles e− = I·t / 96,485; then use mole ratios to get metal deposited
RED CAT / AN OX — reduction at cathode, oxidation at anode (both cell types)
Question bank breakdown
43
2
13 easy · 22 medium · 8 hard
Skills covered
Every question in the bank comes with a per-choice explanation, so you learn why each wrong answer is wrong — not just the key.
Practice this topic
The full set of Applications of Thermodynamics questions — with a per-choice explanation on every answer — lives in the practice workspace. Start free, no account needed.
Study tip
Keep units honest in ΔG = ΔH − TΔS: ΔH is usually kJ/mol while ΔS° is J/(mol·K). Convert ΔS to kJ before subtracting — the exam plants answer choices that punish skipping this step.