Electrochemistry - Chemical Dynamics

Comprehensive vocabulary flashcards covering the key terms, laws, formulas, and principles of Electrochemistry from Module 5: Chemical Dynamics.

Electrochemistry

The branch of chemistry that deals with the conversion of electrical energy into chemical energy and vice versa.

Oxidation (Electronic Concept)

A process in which an atom or ion loses one or more electrons to another species.

Reduction (Electronic Concept)

A process in which an atom or ion gains one or more electrons from another species.

Reducing Agent (Reductant)

A chemical species that loses electrons to another reactant in a reaction, thereby causing the other species to undergo reduction.

Oxidising Agent (Oxidant)

A chemical species that accepts electrons from another reactant in a chemical reaction.

Redox Reaction

A chemical reaction formed by the simultaneous occurrence of oxidation and reduction half-reactions, involving electron transfer.

Oxidation Number (Oxidation State)

The apparent charge that an atom appears to possess when each pair of shared electrons in a heteronuclear covalent bond is assigned to the more electronegative atom.

Electrolyte

A chemical substance whose molten state or aqueous solution conducts electric current through the migration of ions.

Non-electrolyte

A substance whose aqueous solution or liquid state does not conduct electric current.

Electrolytic Conduction

The phenomenon of electrical current conduction through a solution or molten salt mediated by the migration of cations and anions towards oppositely charged electrodes.

Conductance ($L$)

The reciprocal of electrical resistance ($L = \frac{1}{R}$), measured in $\text{ohm}^{-1}$ or siemens ($\text{S}$).

Specific Resistance (Resistivity, $\rho$)

The proportionality constant ($\rho$) in the resistance equation $R = \rho \cdot \frac{l}{A}$, characteristic of the nature of the electrolyte, its concentration, and temperature.

Conductivity ($k$)

The reciprocal of specific resistance ($k = \frac{1}{\rho}$), representing the conducting power of all the ions present in $1\,\text{cm}^3$ of the solution, expressed in $\text{S}\,\text{cm}^{-1}$ or $\text{S}\,\text{m}^{-1}$.

Cell Constant

The geometric ratio of the distance between two parallel electrodes ($l$) to their cross-sectional area ($A$), mathematically represented by $\frac{l}{A}$.

Molar Conductivity ($\lambda_m$)

The conducting power of all the ions furnished by one mole of an electrolyte in a solution of specified concentration, related to conductivity by $\lambda_m = \frac{1000\,k}{M}$ with units of $\text{S}\,\text{cm}^2\,\text{mol}^{-1}$.

Kohlrausch's Law of Independent Migration of Ions

The principle stating that at infinite dilution, each individual ion of an electrolyte makes a definite contribution toward the total molar conductivity of the electrolyte, independent of the nature of other accompanying ions.

Electrochemical Cell

A device comprising two electrodes (anode and cathode) and an electrolyte used for the interconversion of electrical energy and chemical energy.

Electrolytic Cell (Faradaic Cell)

An electrochemical cell in which electrical energy supplied by an external battery drives a non-spontaneous redox reaction at the electrodes.

Galvanic Cell (Voltaic Cell)

An electrochemical cell that produces electrical energy and generates an electromotive force (emf) from spontaneous chemical redox reactions occurring at the electrodes.

Electrolysis

The process of chemical decomposition of an electrolyte into its ions and subsequent discharge of products at the electrodes by passing an electric current.

Faraday's First Law of Electrolysis

The law stating that the mass ($w$) of a substance liberated or deposited at an electrode during electrolysis is directly proportional to the quantity of electricity ($Q$) passed through the electrolyte ($w = zQ = zIt$).

Electrochemical Equivalent ($z$)

The mass of a substance discharged or deposited during electrolysis upon passing a quantity of electricity of $1\,\text{coulomb}$ (or a current of $1\,\text{ampere}$ for $1\,\text{second}$).

Faraday's Second Law of Electrolysis

The law stating that when the same quantity of electricity is passed through different electrolytes connected in series, the masses of different substances liberated are proportional to their chemical equivalent masses.

Discharge Potential (Decomposition Potential)

The minimum potential required for an electrode process (oxidation or reduction) to initiate and proceed during electrolysis.

Over Potential

The excess potential by which the actual observed discharge potential exceeds its theoretical or expected thermodynamic potential, commonly observed during the evolution of gaseous products.

Half Cell

A single electrode compartment consisting of a metal strip immersed in a solution of its own ions where an individual oxidation or reduction process occurs.

Salt Bridge

An inverted U-tube filled with a solidified jelly of agar-agar and an inert electrolyte (such as $\text{KCl}$ or $\text{NH}_4\text{NO}_3$) that completes the inner electrical circuit and maintains electrical neutrality between two half-cells without liquid mixing.

Electrode Potential

The electric potential difference developed at the interface between a metal electrode and the solution containing its own ions when the metal is dipped into it.

Standard Electrode Potential ($E^\circ$)

The potential developed at an electrode under standard conditions: an electrolyte concentration of $1\,\text{M}$, a temperature of $298\,\text{K}$, and a gas pressure of $1\,\text{bar}$.

Standard Hydrogen Electrode (SHE)

A primary reference electrode containing a platinum foil coated with platinum black immersed in $1\,\text{M}\,\text{HCl}$ at $298\,\text{K}$ with pure $\text{H}_2$ gas bubbled at $1\,\text{bar}$, assigned an arbitrary standard potential of $0\,\text{V}$ at all temperatures.

Cell Electromotive Force (Cell emf)

The potential difference between the two half-cell electrodes of a galvanic cell measured in an open circuit (when no current is drawn), calculated as $E_{\text{cell}} = E_{\text{cathode}} - E_{\text{anode}}$.

Electrochemical Series

The arrangement of chemical elements and their electrode reduction reactions in increasing order of their standard reduction potentials ($E^\circ$).

Nernst Equation

A mathematical relationship that calculates the electrode potential or cell emf under non-standard ion concentrations: $E = E^\circ - \frac{2.303\,RT}{nF} \log\left(\frac{1}{[\text{M}^{n+}]}\right)$.

Primary Cell (Dry Cell)

A non-rechargeable electrochemical cell in which chemical reactants are permanently consumed during current discharge, such as the Leclanché dry cell.

Secondary Cell (Lead Storage Battery)

A rechargeable cell or battery that produces electrical energy by spontaneous reactions during discharge and regenerates its original chemical reactants by passing an electric current in reverse during charging.

Fuel Cell

An electrochemical cell that converts the chemical energy of a continuously supplied fuel (such as $\text{H}_2$) and oxidant directly into electrical energy through catalytic electrode reactions.

Standard Gibbs Energy Change ($\Delta G^\circ$)

The thermodynamic measure of the maximum net electrical work that a cell in its standard state can perform, defined by $\Delta G^\circ = -nFE^\circ_{\text{cell}}$.

Corrosion

The gradual deterioration of metals caused by spontaneous electrochemical reactions upon exposure to environmental agents like air and moisture.

Rust

A hydrated form of iron(III) oxide having the formula $\text{Fe}_2\text{O}_3 \cdot x\text{H}_2\text{O}$, formed through the anodic oxidation of iron and cathodic reduction of oxygen in the presence of water.

Galvanisation

A corrosion protection technique wherein an iron surface is coated with a layer of zinc by dipping in molten zinc or via electroplating.

Cathodic Protection (Sacrificial Anode)

A method of corrosion prevention in which a more electropositive metal (such as $\text{Zn}$ or $\text{Mg}$) is connected to or coated onto iron, preferentially oxidizing to protect the iron cathode.