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960 terms · page 15 of 40
Equilibrium Constant
Chemical Equilibrium
Various
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
Equilibrium Constant of a Reversed Reaction
Chemical Equilibrium
Various
The constant obtained when a reaction is written in the opposite direction, equal to the reciprocal of the original.
K_reverse = 1 / K_forward
Equilibrium Constant of a Scaled Reaction
Chemical Equilibrium
Various
The constant obtained when every coefficient in an equation is multiplied by the same factor.
K_new = K_old^n
Equilibrium in Closed Systems
Chemical Equilibrium
Dimensionless
The requirement that no matter enters or leaves for a true chemical equilibrium to be established.
Equilibrium Position
Chemical Equilibrium
mol/L
The particular set of concentrations at which a system settles, describing how far the reaction has proceeded.
Equilibrium Yield
Chemical Equilibrium
Dimensionless
The proportion of reactant converted to product once equilibrium has been reached.
yield = n_product / n_theoretical
Equivalence Point
Acids, Bases & Salts
mol
The point in a titration at which exactly stoichiometric amounts of the two reactants have been combined.
n_acid × basicity = n_base × acidity
Equivalent Weight
Stoichiometry & Chemical Reactions
g/equiv
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
Ester
Organic Chemistry
Dimensionless
A compound formed by replacing the acidic hydrogen of a carboxylic acid with an alkyl group.
R–COO–R′
Esterification
Stoichiometry & Chemical Reactions
Dimensionless
The acid-catalysed condensation of a carboxylic acid with an alcohol to form an ester and water.
RCOOH + R′OH ⇌ RCOOR′ + H₂O
Ether
Organic Chemistry
Dimensionless
A compound in which an oxygen atom is bonded to two carbon atoms.
R–O–R′
Evaporation
States of Matter & Gas Laws
kJ/mol
The escape of molecules from the surface of a liquid into the vapour phase below the boiling point.
Excess Reagent
Stoichiometry & Chemical Reactions
mol
A reactant present in a greater amount than is needed to consume the limiting reagent completely.
n_excess = n_initial − n_reacted
Exergonic Reaction
Thermochemistry & Thermodynamics
kJ/mol
A reaction with a negative Gibbs free energy change, which therefore releases usable energy and proceeds spontaneously.
ΔG < 0
Exothermic Reaction
Stoichiometry & Chemical Reactions
kJ/mol
A reaction that releases energy to the surroundings, giving a negative enthalpy change.
ΔH < 0
Expanded Octet
Chemical Bonding & Molecular Structure
Dimensionless
A bonding arrangement in which a central atom is surrounded by more than eight valence electrons.
Extensive Property
Foundations of Chemistry
Various
A property whose value is directly proportional to the quantity of matter in the sample.
Extent of Reaction
Chemical Equilibrium
mol
A single variable measuring how far a reaction has progressed from pure reactants towards products.
ξ = (n_i − n_i°) / ν_i
f-Block Elements
Atomic Structure & Periodicity
Dimensionless
The lanthanides and actinides, in which electrons fill the f orbitals of the antepenultimate shell.
(n−2)f¹⁻¹⁴
Face-Centred Cubic
States of Matter & Gas Laws
Dimensionless
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
Fajans' Rules
Chemical Bonding & Molecular Structure
Dimensionless
A set of guidelines predicting how much covalent character an ionic bond will have.
Faraday Constant
Electrochemistry & Redox
C/mol
The electric charge carried by one mole of electrons.
F = 96,485 C/mol
Faraday's First Law of Electrolysis
Electrochemistry & Redox
g
The mass of a substance liberated at an electrode is directly proportional to the quantity of electricity passed.
m = Z I t
Faraday's Second Law of Electrolysis
Electrochemistry & Redox
g
When the same quantity of electricity passes through different electrolytes, the masses deposited are proportional to their chemical equivalent weights.
m₁/m₂ = E₁/E₂