Study guides › C/P › General Chemistry
Electrochemistry
Electrochemistry links redox chemistry to voltage, free energy, and electric charge. You will build galvanic and electrolytic cells, calculate cell potentials with the Nernst equation, apply Faraday's laws, and recognize the common batteries.
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What this chapter covers
- Galvanic vs Electrolytic Cells. Half the electrochemistry questions reduce to knowing which electrode is which and which way electrons and ions move.
- Standard Reduction Potentials & Cell Notation. A table of reduction potentials tells you the voltage of any cell and whether a redox reaction is spontaneous.
- Free Energy, the Nernst Equation & Concentration Cells. Voltage, ΔG, and K are three views of the same thing, and the Nernst equation handles non-standard conditions.
- Electrolysis & Faraday's Laws. Faraday's law converts current and time into moles of product, a calculation the MCAT loves.
- Batteries, Fuel Cells & Corrosion. The MCAT asks what happens in common batteries and how voltage and electrode chemistry connect to real devices.
Key points to know
- Anode = oxidation, cathode = reduction, in every cell
- Electrons: anode to cathode; anions: toward anode; cations: toward cathode
- Higher E° = reduced more easily = stronger oxidizing agent
- E°cell = E°cathode − E°anode; positive means spontaneous
- ΔG° = −nFE°; positive E° means negative ΔG°
- E° = (0.0592/n) log K; at equilibrium E = 0 and Q = K
- Q = It; mol e⁻ = Q/F, with F = 96,500 C/mol
- Convert mol e⁻ to mol product using the half-reaction
Try a practice question
At which electrode does oxidation occur in an electrolytic cell, and what is its charge?
- The anode, which is positive
- The cathode, which is negative
- The anode, which is negative
- The cathode, which is positive
Show the answer
A. Oxidation always occurs at the anode. In an electrolytic cell the external source pulls electrons from the anode, making it positive. The negative anode belongs to a galvanic cell.
Common questions
What does this chapter cover?
Electrochemistry covers Galvanic vs Electrolytic Cells, Standard Reduction Potentials & Cell Notation, Free Energy, the Nernst Equation & Concentration Cells, Electrolysis & Faraday's Laws, Batteries, Fuel Cells & Corrosion.
What should I know first?
Anode = oxidation, cathode = reduction, in every cell Electrons: anode to cathode; anions: toward anode; cations: toward cathode Higher E° = reduced more easily = stronger oxidizing agent
24 original practice questions accompany this chapter in the app. Spaced review brings missed ideas back at the right time; it helps memory but cannot promise you will not miss an idea again.