Deep-Dive Guides · Electrochemistry

Electrochemistry — the complete deep dive

One guide dense enough to take you from "I can write the Nernst equation" to CSIR-NET Part-C fluency. The organising idea: electrochemistry is just thermodynamics with a voltmeter. Every equilibrium constant, solubility product, pH and free energy can be read off a cell potential, because ΔG = −nFE.

Free extract — the opening section of the guide, in full.

0. How to use this guide — the master map ▲ top

Every quantitative result in this subject descends from one bridge equation between chemistry and electricity. Fix the map first:

Quantity you want	Route	Master relation
Spontaneity / max work	cell potential → free energy	ΔG = −nFE_cell; ΔG° = −nFE°_cell
Equilibrium constant K	standard EMF	ln K = nFE°/RT (log K = nE°/0.0592 at 298 K)
Potential at any concentration	Nernst equation	E = E° − (RT/nF) ln Q
Solubility product K_sp	a cell whose reaction is the dissolution	same ln K = nFE°/RT
pH	H⁺-sensitive electrode	E = E° − 0.0592 pH when the half-reaction contains as many H⁺ as electrons; in general E = E° − (0.0592 m/n) pH for m H⁺ and n e⁻ (298 K)
Amount deposited/liberated	charge passed	m = (Q/F)(M/n), Q = It
Ionic conductance	additivity of ion contributions	Λ°_m = ν₊λ°₊ + ν₋λ°₋ (Kohlrausch)

The three questions to ask of any electrochemical problem: (1) What is the balanced cell reaction and what is n (electrons transferred)? (2) Is the process at standard state (use E°/K) or at stated concentrations (use Nernst)? (3) Which sign convention am I in? Reduction potentials, cathode − anode, ΔG = −nFE — get these three straight and the arithmetic is routine.

Constants used throughout: F = 96 485 C mol⁻¹; R = 8.314 J K⁻¹ mol⁻¹; at T = 298.15 K, RT/F = 0.02569 V and 2.303 RT/F = 0.05916 V (rounded to 0.0592 V). All standard potentials are reduction potentials versus the SHE unless noted.

Read the rest of this guide

The remaining 9 sections — Conductance & ionic transport, Electrode potentials & galvanic cells, Applications of the Nernst equation, Electrolysis & Faraday's laws and more — are part of ChemVidya Full Access, along with the other guides, the books, the study notes and 6,000+ practice questions with worked solutions.

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