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Abnormal Molar Mass
A molar mass value obtained from colligative measurements that differs from the true value because the solute associates or dissociates.
States of Matter & Gas LawsAbsolute Zero
The lowest possible temperature, at which particles retain only their irreducible quantum zero-point motion.
Foundations of ChemistryAccuracy
The closeness of a measured value to the true or accepted value of the quantity being measured.
Acids, Bases & SaltsAcid
A substance that donates protons, produces hydrogen ions in water, or accepts a pair of electrons.
Acids, Bases & SaltsAcid Dissociation Constant
The equilibrium constant for the ionisation of an acid in water, measuring its strength.
Acids, Bases & SaltsAcid Strength and Molecular Structure
The structural factors that determine how readily a molecule releases a proton.
Acids, Bases & SaltsAcidic Buffer
A buffer made from a weak acid and one of its salts, giving a pH below 7.
Acids, Bases & SaltsAcidic Salt
A salt whose aqueous solution has a pH below 7, or one that still contains replaceable hydrogen.
Acids, Bases & SaltsAcidic Solution
A solution in which the hydrogen ion concentration exceeds the hydroxide ion concentration.
Acids, Bases & SaltsAcid–Base Indicator
A weak acid or base whose conjugate forms have distinctly different colours, used to signal the end point of a titration.
Acids, Bases & SaltsAcid–Base Titration
A titration in which an acid is neutralised by a base, or the reverse, monitored by an indicator or a pH meter.
Chemical Kinetics & CatalysisActivated Complex
The transient arrangement of atoms present at the transition state, poised between reactants and products.
Chemical Kinetics & CatalysisActivation Energy
The minimum energy that colliding particles must possess for a reaction to occur.
Chemical Kinetics & CatalysisActive Site
The specific region of a catalyst or enzyme at which the reacting molecules bind and are transformed.
Chemical EquilibriumActivity
The effective concentration of a species, corrected for non-ideal interactions with its surroundings.
Chemical EquilibriumActivity Coefficient
The factor by which a species' concentration must be multiplied to give its thermodynamic activity.
Stoichiometry & Chemical ReactionsActivity Series
A ranking of metals in order of their tendency to lose electrons and form positive ions.
Stoichiometry & Chemical ReactionsActual Yield
The mass of pure product actually isolated at the end of an experiment.
Biochemistry & Polymer ChemistryAddition Polymerisation
Polymerisation in which unsaturated monomers add to one another with no loss of any atoms.
Stoichiometry & Chemical ReactionsAddition Reaction
A reaction in which two molecules combine to form a single larger product, with no atoms left over.
Biochemistry & Polymer ChemistryAdenosine Triphosphate
The nucleotide that acts as the universal energy currency of living cells.
Thermochemistry & ThermodynamicsAdiabatic Process
A process in which no heat is exchanged between the system and its surroundings.
Chemical Kinetics & CatalysisAdsorption
The accumulation of molecules of a gas or liquid on the surface of a solid.
Solutions & Colligative PropertiesAerosol
A colloidal system in which solid or liquid particles are dispersed in a gas.