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Chemical Equilibrium

Equilibrium Constant

The fixed ratio of product to reactant terms, each raised to its stoichiometric power, that characterises a reaction at a given temperature.

K = Π[products]^ν / Π[reactants]^ν Various
Chemical Equilibrium

Equilibrium Constant of a Reversed Reaction

The constant obtained when a reaction is written in the opposite direction, equal to the reciprocal of the original.

K_reverse = 1 / K_forward Various
Chemical Equilibrium

Equilibrium Constant of a Scaled Reaction

The constant obtained when every coefficient in an equation is multiplied by the same factor.

K_new = K_old^n Various
Chemical Equilibrium

Equilibrium in Closed Systems

The requirement that no matter enters or leaves for a true chemical equilibrium to be established.

Dimensionless
Chemical Equilibrium

Equilibrium Position

The particular set of concentrations at which a system settles, describing how far the reaction has proceeded.

mol/L
Chemical Equilibrium

Equilibrium Yield

The proportion of reactant converted to product once equilibrium has been reached.

yield = n_product / n_theoretical Dimensionless
Acids, Bases & Salts

Equivalence Point

The point in a titration at which exactly stoichiometric amounts of the two reactants have been combined.

n_acid × basicity = n_base × acidity mol
Stoichiometry & Chemical Reactions

Equivalent Weight

The mass of a substance that combines with or displaces 1.008 g of hydrogen, 8 g of oxygen or one mole of electrons.

E = M / n-factor g/equiv
Organic Chemistry

Ester

A compound formed by replacing the acidic hydrogen of a carboxylic acid with an alkyl group.

R–COO–R′ Dimensionless
Stoichiometry & Chemical Reactions

Esterification

The acid-catalysed condensation of a carboxylic acid with an alcohol to form an ester and water.

RCOOH + R′OH ⇌ RCOOR′ + H₂O Dimensionless
Organic Chemistry

Ether

A compound in which an oxygen atom is bonded to two carbon atoms.

R–O–R′ Dimensionless
States of Matter & Gas Laws

Evaporation

The escape of molecules from the surface of a liquid into the vapour phase below the boiling point.

kJ/mol
Stoichiometry & Chemical Reactions

Excess Reagent

A reactant present in a greater amount than is needed to consume the limiting reagent completely.

n_excess = n_initial − n_reacted mol
Thermochemistry & Thermodynamics

Exergonic Reaction

A reaction with a negative Gibbs free energy change, which therefore releases usable energy and proceeds spontaneously.

ΔG < 0 kJ/mol
Stoichiometry & Chemical Reactions

Exothermic Reaction

A reaction that releases energy to the surroundings, giving a negative enthalpy change.

ΔH < 0 kJ/mol
Chemical Bonding & Molecular Structure

Expanded Octet

A bonding arrangement in which a central atom is surrounded by more than eight valence electrons.

Dimensionless
Foundations of Chemistry

Extensive Property

A property whose value is directly proportional to the quantity of matter in the sample.

Various
Chemical Equilibrium

Extent of Reaction

A single variable measuring how far a reaction has progressed from pure reactants towards products.

ξ = (n_i − n_i°) / ν_i mol
Atomic Structure & Periodicity

f-Block Elements

The lanthanides and actinides, in which electrons fill the f orbitals of the antepenultimate shell.

(n−2)f¹⁻¹⁴ Dimensionless
States of Matter & Gas Laws

Face-Centred Cubic

A cubic arrangement with particles at the eight corners and at the centre of each of the six faces.

4 atoms per cell, 74% packing Dimensionless
Chemical Bonding & Molecular Structure

Fajans' Rules

A set of guidelines predicting how much covalent character an ionic bond will have.

Dimensionless
Electrochemistry & Redox

Faraday Constant

The electric charge carried by one mole of electrons.

F = 96,485 C/mol C/mol
Electrochemistry & Redox

Faraday's First Law of Electrolysis

The mass of a substance liberated at an electrode is directly proportional to the quantity of electricity passed.

m = Z I t g
Electrochemistry & Redox

Faraday's Second Law of Electrolysis

When the same quantity of electricity passes through different electrolytes, the masses deposited are proportional to their chemical…

m₁/m₂ = E₁/E₂ g