Browse All 960 Chemistry Terms A–Z

Van der Waals Equation States of Matter & Gas Laws Various A modified equation of state that corrects the ideal gas law for molecular volume and intermolecular attraction. (p + an²/V²)(V − nb) = nRT

Van der Waals Forces Chemical Bonding & Molecular Structure kJ/mol The collective name for the weak attractive forces between molecules arising from dipole interactions. E ∝ 1 / r⁶

Van't Hoff Equation Chemical Equilibrium kJ/mol The equation describing how an equilibrium constant varies with temperature. ln(K₂/K₁) = −ΔH°/R (1/T₂ − 1/T₁)

Van't Hoff Factor Solutions & Colligative Properties Dimensionless The ratio of the actual number of particles produced in solution to the number of formula units dissolved. i = observed ΔT / calculated ΔT

Vapour Pressure States of Matter & Gas Laws Pa The pressure exerted by a vapour in dynamic equilibrium with its liquid or solid at a given temperature. ln p = −ΔH_vap / RT + C

Vapour–Liquid Equilibrium Chemical Equilibrium Pa The equilibrium between a liquid and its vapour in a closed container at a given temperature. p = p_saturated

Viscosity States of Matter & Gas Laws Pa·s A liquid's resistance to flow, arising from internal friction between adjacent layers of molecules. F = ηA (dv/dx)

Vitamin Biochemistry & Polymer Chemistry mg An organic compound required in small amounts that an organism cannot synthesise for itself.

Volume Percentage Solutions & Colligative Properties Dimensionless The volume of a liquid solute expressed as a percentage of the total volume of solution. % v/v = (V_solute / V_solution) × 100

Volumetric Analysis Analytical Chemistry & Spectroscopy mL Quantitative analysis based on measuring the volume of a standard solution needed to react with the analyte. n = M × V

VSEPR Theory Chemical Bonding & Molecular Structure Dimensionless The model that predicts molecular shape by arranging valence electron pairs around a central atom so their mutual repulsion is minimised. AXₘEₙ notation

Vulcanisation Biochemistry & Polymer Chemistry Dimensionless The treatment of natural rubber with sulfur to form cross-links that greatly improve its properties.

Water of Crystallisation Foundations of Chemistry mol per mol Water molecules chemically bound within the crystal lattice of a hydrated salt in a fixed stoichiometric ratio.

Weak Acid Acids, Bases & Salts mol/L An acid that ionises only partially in aqueous solution, establishing an equilibrium with its conjugate base. HA ⇌ H⁺ + A⁻

Weak Base Acids, Bases & Salts mol/L A base that accepts protons only partially in aqueous solution, establishing an equilibrium. B + H₂O ⇌ BH⁺ + OH⁻

Weak Field Ligand Inorganic & Coordination Chemistry cm⁻¹ A ligand that produces only a small crystal field splitting, so electrons occupy upper orbitals rather than pairing. Δ < P

Werner's Theory Inorganic & Coordination Chemistry Dimensionless The 1893 theory proposing that metals exhibit two types of valence and that ligands occupy fixed positions in space around the metal.

Work Thermochemistry & Thermodynamics J Energy transferred when a force moves through a distance, most often in chemistry as a gas expanding against external pressure. w = −p_ext ΔV

X-ray Crystallography Analytical Chemistry & Spectroscopy pm A technique that determines the three-dimensional atomic structure of a crystal from its X-ray diffraction pattern. nλ = 2d sin θ

Zaitsev's Rule Organic Chemistry Dimensionless In an elimination reaction, the major product is usually the more highly substituted and therefore more stable alkene.

Zero-Order Reaction Chemical Kinetics & Catalysis mol/(L·s) A reaction whose rate is independent of the concentration of the reactant. [A] = [A]₀ − kt

Zeroth Law of Thermodynamics Thermochemistry & Thermodynamics K If two systems are each in thermal equilibrium with a third, they are in thermal equilibrium with each other. T_A = T_C and T_B = T_C ⟹ T_A = T_B

Zone Refining Inorganic & Coordination Chemistry Dimensionless An ultra-purification technique in which a narrow molten zone is passed repeatedly along a solid rod.

Zwitterion Biochemistry & Polymer Chemistry Dimensionless A molecule carrying both a positive and a negative charge but no net overall charge. ⁺H₃N–CHR–COO⁻

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