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Uncertainty Principle the characteristic that any measurement involves estimates and cannot be exactly reproduced
Unimolecular step a reaction step involving only one molecule
Unit cell he smallest repeating unit of a lattice
Unit factor an equivalence statement between units used for converting from one unit to another
Universal gas constant the combined proportionality constant in the ideal gas law; 0.08206 L atm/K mol or 8.3145 J/K mol
Useful Work Work other than pressure-volune work that is obtainable from a system
Valence The chemical conbining capacity of an element or ion
Valence Band In a metal, the highest energy band of molecular orbitals that is filled with electrons
Valence Bond Model The description of covalent bonding as the result of the overlap of atomic orbitals each of which contains an unpaired electron
Valence electrons the electrons in the outermost principal quantum level of an atom
Valence shell electron pair repulsion (VSEPR) model a model whose main postulate is that the structure around a given atom in a molecule is determined principally by minimizing electron-pair repulsions
van der Waals's equation a mathematical expression for describing the behavior of real gases
van't Hoff factor the ratio of moles of particles in solution to moles of solute dissolved
Vaporization The conversion of a liquid or solid to a vapor
Vapor pressure the pressure of the vapor over a liquid at equilibrium
Vibrational Spectra Absorption spectra resulting from the excitation of molecules between vibrational energy states; infrared spectra
Viscosity The resistance of a liquid to flow
Volatile Having a relatively high vapor pressure and a relatively low boiling point
Volt the unit of electrical potential defined as one joule of work per coulomb of charge transferred
Voltaic Cell An electrochemical cell that releases electric energy as the result of a spontaneous oxidation- reduction reaction also called a galvanic cell
Voltmeter an instrument that measures cell potential by draw
ing electric current through a known resistance
Volumetric analysis process involving titration of one solution with another
Vulcanization a process in which sulfur is added to rubber and the mixture is heated, causing crosslinking of the polymer chains and thus adding strength to the rubber

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