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960 terms · page 4 of 40
Average Rate
Chemical Kinetics & Catalysis
mol/(L·s)
The overall change in concentration divided by the total time interval over which it occurred.
rate_avg = Δ[A] / Δt
Avogadro's Law
States of Matter & Gas Laws
L/mol
Equal volumes of all gases at the same temperature and pressure contain equal numbers of molecules.
V ∝ n
Avogadro's Number
Foundations of Chemistry
mol⁻¹
The number of elementary entities in one mole of substance, fixed by definition at 6.02214076 × 10²³ mol⁻¹.
N = n × N_A
Azeotrope
Solutions & Colligative Properties
°C
A liquid mixture that boils at constant temperature and distils without any change in composition.
Azimuthal Quantum Number
Atomic Structure & Periodicity
Dimensionless
The quantum number l that determines the shape of an orbital and the magnitude of the electron's orbital angular momentum.
l = 0 to (n − 1)
Back Bonding
Chemical Bonding & Molecular Structure
kJ/mol
The donation of electron density from a filled orbital on one atom into an empty orbital on its bonded partner, in the direction opposite to the sigma bond.
M(dπ) → L(π*)
Back Titration
Analytical Chemistry & Spectroscopy
mol
A technique in which excess reagent is added and the unreacted portion titrated to find how much reacted with the analyte.
n_reacted = n_added − n_remaining
Background Radiation
Nuclear & Radiochemistry
mSv/year
The ionising radiation always present in the environment from natural and artificial sources.
Balanced Chemical Equation
Stoichiometry & Chemical Reactions
Dimensionless
An equation in which the number of atoms of each element and the total charge are identical on both sides.
Σ atoms(left) = Σ atoms(right)
Band of Stability
Nuclear & Radiochemistry
Dimensionless
The region on a plot of neutron number against proton number within which stable nuclides are found.
Base
Acids, Bases & Salts
Dimensionless
A substance that accepts protons, produces hydroxide ions in water, or donates a pair of electrons.
B + H⁺ → BH⁺
Base Dissociation Constant
Acids, Bases & Salts
mol/L
The equilibrium constant for the reaction of a base with water to produce hydroxide ions.
Kb = [BH⁺][OH⁻] / [B]
Base Pairing
Biochemistry & Polymer Chemistry
Dimensionless
The specific hydrogen bonding between complementary nitrogenous bases in nucleic acids.
A–T (2 H-bonds), G–C (3 H-bonds)
Base Peak
Analytical Chemistry & Spectroscopy
Dimensionless
The most intense peak in a mass spectrum, assigned an arbitrary relative abundance of 100%.
Basic Buffer
Acids, Bases & Salts
Dimensionless
A buffer made from a weak base and one of its salts, giving a pH above 7.
pOH = pKb + log([salt]/[base])
Basic Salt
Acids, Bases & Salts
Dimensionless
A salt whose aqueous solution has a pH above 7, or one that retains a hydroxide group.
Basic Solution
Acids, Bases & Salts
mol/L
A solution in which the hydroxide ion concentration exceeds the hydrogen ion concentration.
[OH⁻] > [H⁺]
Becquerel
Nuclear & Radiochemistry
Bq
The SI unit of radioactivity, equal to one nuclear disintegration per second.
1 Bq = 1 s⁻¹
Beer–Lambert Law
Analytical Chemistry & Spectroscopy
Dimensionless
The relation stating that absorbance is proportional to concentration and to the path length of the sample.
A = ε c l
Bent Geometry
Chemical Bonding & Molecular Structure
degrees
A molecular shape in which two bonded atoms form an angle at a central atom that also carries one or more lone pairs.
AX₂E or AX₂E₂
Benzene
Organic Chemistry
Dimensionless
The simplest aromatic hydrocarbon, a planar regular hexagon of six sp² carbons with a delocalised pi cloud.
C₆H₆
Beta-Minus Decay
Nuclear & Radiochemistry
MeV
Radioactive decay in which a neutron converts into a proton, emitting an electron and an antineutrino.
n → p + e⁻ + ν̄
Bidentate Ligand
Inorganic & Coordination Chemistry
Dimensionless
A ligand that binds to the same metal centre through two donor atoms, forming a ring.
Bimolecular Reaction
Chemical Kinetics & Catalysis
L/(mol·s)
An elementary step in which two species collide and react.
A + B → products, rate = k[A][B]