Chemistry terms starting with S

Standard Temperature and Pressure Foundations of Chemistry K, kPa A defined reference condition used to report and compare gas measurements, currently 0 °C and 100 kPa under IUPAC. T = 273.15 K, p = 100 kPa

Standardisation Analytical Chemistry & Spectroscopy mol/L The determination of the exact concentration of a solution by titrating it against a primary standard. M₁V₁ / n₁ = M₂V₂ / n₂

Starch Biochemistry & Polymer Chemistry Dimensionless The storage polysaccharide of plants, consisting of amylose and amylopectin. (C₆H₁₀O₅)ₙ

State Function Thermochemistry & Thermodynamics Various A property whose value depends only on the current state of the system, not on how that state was reached. ΔX = X_final − X_initial

Static Equilibrium Chemical Equilibrium Dimensionless A state of no change in which the opposing processes have genuinely ceased rather than balancing.

Stationary Phase Analytical Chemistry & Spectroscopy Dimensionless The fixed material in a chromatographic system with which the sample components interact as they pass.

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

Terms starting with S