Entropy (S)
Measure of energy dispersal or microstates. Increases with more particles, higher T, or greater volume.
Example: Dissolving NaCl: S increases as ordered crystal becomes dispersed ions.
Adaptive
Learn Thermodynamics and Electrochemistry
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Session Length
~17 min
Adaptive Checks
15 questions
Transfer Probes
8
Lesson Notes
Thermodynamics predicts whether reactions are spontaneous through entropy and Gibbs free energy. Entropy (S) measures disorder and increases in processes that spread energy. Gibbs free energy (G=H-TS) combines enthalpy and entropy to determine spontaneity: negative delta-G means spontaneous.
Electrochemistry links thermodynamics to electron transfer: galvanic cells produce electricity from spontaneous redox reactions, while electrolytic cells use electricity to drive non-spontaneous reactions. Covers entropy, Gibbs free energy, spontaneity, galvanic and electrolytic cells, standard reduction potentials, Nernst equation, and Faraday law for AP Chemistry Unit 9.
You'll be able to:
- Predict entropy changes based on particle count, phase, and temperature
- Calculate Gibbs free energy and determine spontaneity from delta-G, delta-H, and delta-S
- Relate standard cell potential to delta-G and equilibrium constant K
- Diagram and explain galvanic (voltaic) and electrolytic cells
- Apply Faraday law to calculate mass deposited in electrolysis
One step at a time.
Interactive Exploration
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Key Concepts
Gibbs Free Energy
G=H-TS. delta-G<0: spontaneous. delta-G>0: non-spontaneous. delta-G=0: equilibrium.
Example: Ice melting at 25C: delta-G<0, spontaneous.
Standard Cell Potential
E-cell = E-cathode - E-anode. Positive E-cell means spontaneous galvanic cell.
Example: Zn/Cu cell: E=+1.10V.
Galvanic Cell
Electrochemical cell where spontaneous redox reaction produces electric current.
Example: Daniell cell: Zn anode, Cu cathode, salt bridge.
Electrolytic Cell
Uses external current to drive non-spontaneous redox reaction.
Example: Electrolysis of water: 2H2O->2H2+O2.
Nernst Equation
E=E0-(RT/nF)lnQ adjusts cell potential for non-standard conditions.
Example: At non-standard concentrations, E differs from E0.
Faraday Law
Mass deposited = (ItM)/(nF). Links charge to moles of substance.
Example: Plating Cu: 2 mol e- per mol Cu deposited.
Second Law of Thermodynamics
Total entropy of universe increases for spontaneous processes.
Example: Heat flows from hot to cold, increasing universal entropy.
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Concept Map
See how the key ideas connect. Nodes color in as you practice.
Worked Example
Walk through a solved problem step-by-step. Try predicting each step before revealing it.
Adaptive Practice
This is guided practice, not just a quiz. Hints and pacing adjust in real time.
Small steps add up.
What you get while practicing:
- Math Lens cues for what to look for and what to ignore.
- Progressive hints (direction, rule, then apply).
- Targeted feedback when a common misconception appears.
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