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960 terms · page 37 of 40
Steady-State Approximation
Chemical Kinetics & Catalysis
mol/L
The assumption that the concentration of a reactive intermediate stays essentially constant because it is consumed as fast as it is formed.
d[intermediate]/dt ≈ 0
Stepwise Formation Constant
Chemical Equilibrium
Various
The equilibrium constant for the addition of one further ligand to a partially formed complex.
K₁, K₂, K₃ …
Stepwise Ionisation
Acids, Bases & Salts
mol/L
The successive loss of protons from a polyprotic acid, each governed by its own equilibrium constant.
Ka₁ ≫ Ka₂ ≫ Ka₃
Stereoisomerism
Organic Chemistry
Dimensionless
Isomerism in which molecules have identical connectivity but differ in the spatial arrangement of their atoms.
Steric Factor
Chemical Kinetics & Catalysis
Dimensionless
The fraction of sufficiently energetic collisions that also have the correct spatial orientation for reaction.
p = A / Z
Steroid
Biochemistry & Polymer Chemistry
Dimensionless
A lipid built on a characteristic framework of three six-membered rings fused to one five-membered ring.
C₁₇ tetracyclic core
Stock Solution
Solutions & Colligative Properties
mol/L
A concentrated solution prepared in advance and stored for later dilution to working strength.
Stoichiometric Coefficient
Stoichiometry & Chemical Reactions
Dimensionless
The number written before a formula in a balanced equation, giving the relative amount of that substance consumed or produced.
Stoichiometric Mixture
Stoichiometry & Chemical Reactions
mol
A mixture of reactants present in exactly the proportions required by the balanced equation, with no reactant in excess.
n_A : n_B = a : b
Stoichiometry
Stoichiometry & Chemical Reactions
mol
The quantitative study of the mass and mole relationships between reactants and products in a chemical reaction.
n_A / a = n_B / b
Strong Acid
Acids, Bases & Salts
mol/L
An acid that ionises essentially completely in aqueous solution.
HA → H⁺ + A⁻ (complete)
Strong Base
Acids, Bases & Salts
mol/L
A base that dissociates or ionises completely in aqueous solution to give hydroxide ions.
BOH → B⁺ + OH⁻
Strong Field Ligand
Inorganic & Coordination Chemistry
cm⁻¹
A ligand that produces a large crystal field splitting, favouring electron pairing over occupation of upper orbitals.
Δ > P
Strong Nuclear Force
Nuclear & Radiochemistry
N
The short-range attractive force that binds protons and neutrons together within the nucleus.
Structural Formula
Foundations of Chemistry
Dimensionless
A representation showing how the atoms in a molecule are connected and, often, how they are arranged in space.
Structural Isomerism
Organic Chemistry
Dimensionless
Isomerism in which the compounds differ in the order in which their atoms are connected.
Sublimation
States of Matter & Gas Laws
kJ/mol
The direct conversion of a solid into a vapour without passing through the liquid state.
ΔH_sub = ΔH_fus + ΔH_vap
Substitution Reaction
Stoichiometry & Chemical Reactions
Dimensionless
A reaction in which one atom or group in a molecule is replaced by another.
R–X + Y → R–Y + X
Successive Ionisation Energies
Atomic Structure & Periodicity
kJ/mol
The series of energies required to remove electrons one after another from the same atom.
IE₁ < IE₂ < IE₃ …
Superacid
Acids, Bases & Salts
Dimensionless
An acid stronger than pure sulfuric acid, capable of protonating species normally regarded as completely non-basic.
H₀ < −12
Supercritical Fluid
States of Matter & Gas Laws
K, Pa
A substance held above both its critical temperature and critical pressure, where liquid and gas phases are indistinguishable.
T > T_c and p > p_c
Supersaturated Solution
Solutions & Colligative Properties
mol/L
An unstable solution containing more dissolved solute than the equilibrium solubility at that temperature.
Surface Tension
States of Matter & Gas Laws
N/m
The energy required to increase the surface area of a liquid by unit amount, arising from unbalanced intermolecular forces at the surface.
γ = F / L
Surroundings
Thermochemistry & Thermodynamics
Dimensionless
Everything outside the chosen system with which it can exchange energy or matter.