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Biochemistry & Polymer Chemistry

Glycosidic Bond

The covalent linkage joining a sugar unit to another molecule through an oxygen bridge.

C–O–C Dimensionless
States of Matter & Gas Laws

Graham's Law of Diffusion

The rate at which a gas diffuses or effuses is inversely proportional to the square root of its molar mass.

r₁ / r₂ = √(M₂ / M₁) Dimensionless
Analytical Chemistry & Spectroscopy

Gravimetric Analysis

Quantitative analysis based on measuring the mass of a product of known composition.

% analyte = (m_precipitate × factor / m_sample) × 100 g
Nuclear & Radiochemistry

Gray

The SI unit of absorbed radiation dose, equal to one joule of energy deposited per kilogram of matter.

1 Gy = 1 J/kg Gy
Organic Chemistry

Grignard Reagent

An organomagnesium halide that acts as a source of a carbanion-like nucleophilic carbon.

R–Mg–X Dimensionless
Atomic Structure & Periodicity

Group

A vertical column of the periodic table whose members share the same valence electron configuration.

Dimensionless
Chemical Kinetics & Catalysis

Half-Life of a Reaction

The time required for the concentration of a reactant to fall to half its initial value.

t½ = 0.693 / k (first order) s
Electrochemistry & Redox

Half-Reaction

An equation showing either the oxidation or the reduction part of a redox process, including the electrons transferred.

Ox + n e⁻ ⇌ Red Dimensionless
Stoichiometry & Chemical Reactions

Half-Reaction Method

A technique for balancing redox equations by splitting them into separate oxidation and reduction half-equations.

balance atoms, then O with H₂O, H with H⁺, charge with e⁻ Dimensionless
Organic Chemistry

Haloalkane

An alkane in which one or more hydrogen atoms have been replaced by halogen atoms.

R–X (X = F, Cl, Br, I) Dimensionless
Atomic Structure & Periodicity

Halogens

The group 17 elements — fluorine through astatine — which are one electron short of a full outer shell.

ns² np⁵ Dimensionless
Thermochemistry & Thermodynamics

Heat

Energy transferred between a system and its surroundings solely because of a temperature difference.

q = mcΔT J
Thermochemistry & Thermodynamics

Heat Capacity at Constant Pressure

The heat needed to raise a system's temperature by one kelvin while pressure is held constant.

C_p = C_V + R (ideal gas) J/(mol·K)
Thermochemistry & Thermodynamics

Heat Capacity at Constant Volume

The heat needed to raise a system's temperature by one kelvin while its volume is held fixed.

C_V = (∂U/∂T)_V J/(mol·K)
Atomic Structure & Periodicity

Heisenberg Uncertainty Principle

The principle that the position and momentum of a particle cannot both be known to arbitrary precision at the same time.

Δx · Δp ≥ h / 4π J·s
Thermochemistry & Thermodynamics

Helmholtz Free Energy

The thermodynamic potential that determines spontaneity at constant temperature and volume.

A = U − TS kJ/mol
Acids, Bases & Salts

Henderson–Hasselbalch Equation

The equation giving the pH of a buffer from the pKa of its acid and the ratio of conjugate base to acid.

pH = pKa + log([A⁻]/[HA]) Dimensionless
Solutions & Colligative Properties

Henry's Law

The solubility of a gas in a liquid is directly proportional to the partial pressure of that gas above the liquid.

p = K_H × x Pa
Thermochemistry & Thermodynamics

Hess's Law

The total enthalpy change of a reaction is the same regardless of the route taken, provided the initial and final states are identical.

ΔH_total = ΣΔH_steps kJ/mol
Chemical Kinetics & Catalysis

Heterogeneous Catalysis

Catalysis in which the catalyst is in a different phase from the reactants, usually a solid with gaseous or liquid reagents.

Dimensionless
Chemical Equilibrium

Heterogeneous Equilibrium

An equilibrium involving species present in more than one phase.

Dimensionless
Foundations of Chemistry

Heterogeneous Mixture

A mixture in which the components remain physically distinct, so composition varies from one region of the sample to another.

Dimensionless
States of Matter & Gas Laws

Hexagonal Close Packing

A close-packed arrangement in which layers of spheres repeat in an ABAB sequence.

6 atoms per cell, 74% packing Dimensionless
Inorganic & Coordination Chemistry

High Spin Complex

A complex in which electrons occupy the higher d orbitals singly before pairing, maximising unpaired spins.

Δ < P BM