CHM101 – Electrochemistry Vocabulary

Vocabulary flashcards covering key terms and definitions from CHM101 Electrochemistry lecture notes.

Electrochemistry

Branch of chemistry that studies the interchange between chemical reactions and electrical energy.

Galvanic (Voltaic) Cell

Electrochemical cell in which a spontaneous redox reaction produces electric current.

Electrolytic Cell

Cell in which an external electric current drives a non-spontaneous chemical reaction (electrolysis).

Redox Reaction

Reaction involving simultaneous oxidation (loss of electrons) and reduction (gain of electrons).

Anode (Galvanic Cell)

Electrode where oxidation occurs; negative terminal in a galvanic cell.

Cathode (Galvanic Cell)

Electrode where reduction occurs; positive terminal in a galvanic cell.

Anode (Electrolytic Cell)

Positive electrode where oxidation is forced by external power supply.

Cathode (Electrolytic Cell)

Negative electrode where reduction is forced by external power supply.

Electrode

Conductive surface on which half-reactions (oxidation or reduction) take place.

Inert Electrode

Electrode (e.g., Pt) that does not participate chemically in the cell reaction.

Salt Bridge

Ionic medium that completes the circuit, maintains charge balance, and prevents mixing of solutions in a galvanic cell.

EMF (Electromotive Force)

Voltage difference between two electrodes of a cell; also called cell potential (E).

Standard Conditions

Reference state of 1 M solute concentration, 1 atm gas pressure, and 25 °C (298 K).

Standard Cell Potential (E°)

Cell potential measured under standard conditions; denoted with a superscript °.

Cell Notation

Shorthand representation of a galvanic cell using vertical bars for phase boundaries and || for the salt bridge.

Standard Hydrogen Electrode (SHE)

Reference electrode assigned E° = 0.00 V; involves H₂(g, 1 atm)/H⁺(1 M) with Pt electrode.

Standard Electrode (Reduction) Potential

Potential of a half-cell relative to the SHE when written as a reduction reaction.

Electrochemical Series

Ordered list of elements/ions by their standard reduction potentials, indicating oxidizing/reducing strength.

Oxidizing Agent

Species that gains electrons (is reduced); strength increases with more positive E° value.

Reducing Agent

Species that loses electrons (is oxidized); strength increases with more negative E° value.

Nernst Equation

Expression relating cell potential to standard potential and reaction quotient: E = E° – (0.0591/n) log Q at 25 °C.

Reaction Quotient (Q)

Ratio of product to reactant activities at a given moment; used in the Nernst equation.

Concentration Cell

Cell composed of identical electrodes/solutions differing only in ion concentration; E depends on concentration gradient.

Gibbs Free Energy (ΔG)

Thermodynamic quantity that indicates spontaneity; related to cell potential by ΔG = –nF E.

Faraday Constant (F)

Charge of one mole of electrons; approximately 96 487 C mol⁻¹.

Corrosion

Undesired oxidation of metals by environmental agents, often involving O₂ and moisture.

Sacrificial Anode

More active metal attached to a structure to preferentially corrode and protect the structure (cathodic protection).

Cathodic Protection

Technique of preventing corrosion by making the metal surface act as a cathode, often via sacrificial anodes or impressed current.

Leclanché (Dry) Cell

Primary battery using Zn anode, MnO₂/NH₄Cl paste cathode, and producing ~1.5 V.

Lead Storage Battery

Rechargeable battery using Pb/PbO₂ electrodes in 40 % H₂SO₄; E° ≈ 2.04–2.40 V per cell.

Electrolysis

Process of driving a non-spontaneous chemical change with electrical energy.

Electrorefining

Purification of metals (e.g., copper) by electrolytic deposition from impure anode onto pure cathode.

Faraday’s First Law

Mass of substance deposited is proportional to the quantity of electricity passed (Q = It).

Faraday’s Second Law

For the same charge, masses of elements deposited are proportional to their equivalent masses.

Equivalent Mass

Molar mass divided by the number of electrons exchanged per ion in redox deposition.

Cell Potential Significance

E > 0: forward reaction spontaneous; E = 0: equilibrium; E < 0: reverse reaction favored.

Half-Reaction

One part of a redox reaction—either oxidation or reduction—written separately to show electron transfer.

Emf Measurement

Determined with a voltmeter connected across the electrodes under open-circuit conditions.

Phase Boundary (|)

Vertical bar in cell notation indicating a change in phase or concentration within one half-cell.

Salt Bridge Symbol (||)

Double vertical line in cell notation representing the salt bridge between half-cells.

Oxidation Number Change

Increase at anode (oxidation), decrease at cathode (reduction) in a galvanic cell.

Free Energy–Equilibrium Constant Relation

ΔG° = –RT ln K; combines thermodynamics with electrochemical data.

Primary Cell

Battery designed for single discharge; cannot be recharged effectively (e.g., Leclanché cell).

Secondary Cell

Rechargeable battery in which cell reactions are reversible (e.g., lead-acid battery).

Overpotential

Extra voltage required above theoretical E° to drive an electrochemical reaction at practical rates.

Industrial Copper Purification

Electrolytic process where impure Cu anode dissolves and pure Cu plates onto cathode in CuSO₄ solution.