Build galvanic and electrolytic cells, look up standard reduction potentials, and apply the Nernst equation.
Electrochemistry bridges thermodynamics and chemical reactions by quantifying the electrical work that oxidation-reduction reactions can perform. It is a major topic in AP Chemistry Unit 9, consistently tested in USNCO Part II free response questions, and a core IChO theoretical domain.
Standard reduction potentials (E°) measure the tendency of a half-reaction to proceed as a reduction relative to the standard hydrogen electrode (SHE), defined as 0.00 V. A more positive E° means a stronger oxidizing agent. To build a galvanic cell, pair a reduction half-reaction (cathode) with an oxidation half-reaction (anode, reverse the sign of E°): E°cell = E°cathode − E°anode.
The standard cell potential connects to thermodynamics via ΔG° = −nFE°cell, where n is the moles of electrons transferred and F is Faraday's constant (96,485 C/mol). A positive E°cell gives a negative ΔG° — confirming the cell reaction is spontaneous. The equilibrium constant K is related by ΔG° = −RT ln K, completing the triangle: E°cell, ΔG°, and K are all interconvertible.
At non-standard conditions, the Nernst equation applies: E = E° − (RT/nF) ln Q = E° − (0.0592/n) log Q at 25°C. As a cell discharges, reactant concentrations fall and product concentrations rise, increasing Q and decreasing E. When E = 0, the cell is at equilibrium and Q = K.
Electrolytic cells use an external power source to drive non-spontaneous reactions. Faraday's laws of electrolysis state that the mass of substance deposited is proportional to the charge passed: m = (MIt)/(nF), where M is molar mass, I is current, t is time, n is electrons per ion, and F is Faraday's constant. Electroplating, chlor-alkali production, and aluminum smelting all rely on electrolysis.
This electrochemical cell simulator lets you select half-reactions, build galvanic and electrolytic cells, apply the Nernst equation with adjustable concentration sliders, and calculate Faraday's law quantities — the complete AP Chemistry and USNCO electrochemistry toolkit.