Quant. Analysis – Flashcards
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| Enthalpy Change |
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| heat absorbed or released when a rxn. occurs at constant pressure |
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| Endothermic Rxn. |
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| one for which delta H is positive, heat must be supplied to reactants for them to react |
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| Exothermic Rxn. |
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| one for which delta H is negative, heat is liberated when products formed |
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| Entropy |
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| a measure of the "disorder" of a substance |
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| Gibbs Free Energy |
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| for any process at constant temp. is related to change in enthalpy, determines if there's net driving force for reactants or products to be formed |
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| Le Chatelier's Principle |
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| if a system at equilibrium's disturbed, the direction it proceeds back to equilibrium is such that disturbance is partly offset |
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| Rxn. Quotient Q |
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| expression having same form as equilibrium constant for rxn. |
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| Solubility Product Ksp |
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| equilibrium constant for dissociation of solid salt to give its ions in soln. |
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| Common Ion Effect |
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| occurs when salt's dissolved in soln. already containing one of the ions of salt, application of Le Chatelier's Principle |
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| Coprecipitation |
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| occurs when substance whose solubility not exceeded precipitates along w/one whose solubility is exceeded |
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| Complex Ions |
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| ions containing two + ions or molecules that are each stable by themselves |
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| Ligand |
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| an atom or group attached to central atom in molecule, or attached to anything else of interest |
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| Lewis Acid |
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| e- acceptor |
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| Lewis Base |
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| e- donor |
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| Adduct |
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| product formed when Lewis Base combines w/Lewis Acid |
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| Arrhenius Acid |
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| produces hydronium ion or H30+ in aqueous solns. |
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| Arrhenius Base |
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| produces OH- in aqueous solns. |
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| Bronsted-Lowry Acid |
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| a proton donor |
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| Bronsted-Lowry Base |
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| a proton acceptor |
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| Salt |
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| an ionic solid |
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| Autoprotolysis |
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| rxn. which 2 molecules of same species transfer a proton from one to the other |
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| Protic Solvents |
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| ones w/acidic H atoms |
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| Aprotic Solvents |
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| ones that cannot donate protons in an acid-base rxn. |
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| Polyprotic Acids and Bases |
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| compounds that can donate or accept more than one proton |
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| Acid |
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| substance that inc. the concentration of H+ when added to water |
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| Acidic Soln. |
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| one which activity of H+ > activity of OH- |
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| Base |
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| substance that dec. the concentration of H+ when added to water |
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| Basic Soln. |
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| one which activity of OH- > activity of H+ |
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| Spectroscopy |
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| study of interaction of light and matter |
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| Spectrophotometry |
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| any method using light to measure chemical concentrations |
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| Electromagnetic Spectrum |
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| whole range of electromagnetic radiation, including visible light, radio waves, x-rays, etc. |
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| Planck's Constant |
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| fundamental constant of nature equal to energy of light divided by freq. |
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| Ground State |
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| state of atom/molecule w/minimum possible energy |
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| Excited State |
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| any state of atom/molecule having more than minimum possible energy |
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| Photon |
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| particle of light w/energy hv (h = Planck's constant and v = freq.) |
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| Irradiance |
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| power per unit area of beam of electromagnetic radiation |
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| Transmittance |
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| radiant power go light striking sample on one side divided by radiant power of light emerging from other side of sample |
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| Absorbance |
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| logarithmic comparison of radiant power of light on one side divided by radiant power of light emerging from other side |
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| Beer-Lambert Law |
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| relates absorbance of sample to concentration, pathlength, and molar absorptivity |
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| Cuvet |
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| cell w/transparent walls used to hold samples for spectrophotometric measurements |
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| Spectrophotometric Analysis |
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| any method which light absorption, emission, reflection, pr scattering's used to measure chemical concentrations |
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| Spectrophotometric Titrations |
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| one which absorption of light's used to monitor progress of titration rxn. and to find equilibrium pt. |
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| Molecular Orbitals |
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| describes distribution of an e- w/in a molecule |
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| Electronic Transition |
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| one which e- is promoted from one energy level to another |
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| Singlet State |
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| one which all e- spins are paired |
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| Triplet State |
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| electronic state which there are two unpaired e- |
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| Vibrational Transition |
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| occurs when molecule changes its vibrational energy |
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| Rotational Transition |
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| occurs when molecule changes its rotational energy |
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| Internal Conversion |
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| radiationless, isoenergetic, electronic transition b/w states of same e- spin multiplicity |
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| Intersystem Crossing |
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| radiationless, isoenergetic, electronic transition b/s states of diff. e- spin multiplicity |
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| Fluorescence |
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| process which molecule emits photon after absorbing photon and results from transition b/w states of same spin multiplicity |
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| Phosphorescence |
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| emission of light during transition b/w states of diff. spin multiplicity, and is slower than fluorescence |
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| Luminescence |
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| any emission of light by a molecule |
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| Chemiluminescence |
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| emission of light by an excited-state product of chemical rxn. |
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| Immiscible |
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| 2 liquids that do not form a single phase when mixed together |
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| Miscible |
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| 2 liquids that form a single phase when mixed in any ratio |
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| Solvent Extraction |
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| method in which chemical species transferred from one liquid phase to another, used to separate components of a mixture |
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| Extraction |
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| process which solute's transferred from one phase to another |
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| Chromatography |
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| technique in which molecules in mobile phase separated bc of their diff. affinities for a stationary phase |
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| Mobile Phase |
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| in chromatography, phase that travels through column |
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| Stationary Phase |
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| in chromatography, phase that does not move through column |
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| Eluent |
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| solvent applied to beginning of chromatography column |
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| Eluate |
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| what comes out of chromatography column |
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| Elution |
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| process of passing a liquid or gas through a chromatography column |
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| Packed Column |
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| chromatography column filled w/stationary phase particles |
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| Open Tubular Column |
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| in chromatography, capillary column whose walls are coated w/stationary phase |
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| Adsorption Chromatography |
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| technique in which solute equilibrates b/w mobile phase and adsorption sites on stationary phase |
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| Partition Chromatography |
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| technique in which separation's achieved by equilibration of solute b/w phases |
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| Ion-Exchange Chromatography |
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| technique in which solute ions retained by oppositely charged sites in stationary phase |
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| Molecular Exclusion Chromatography |
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| technique in which stationary phase has porous structure into which sm. molecules can enter but lg. molecules cannot, so lg. molecules move faster |
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| Affinity Chromatography |
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| technique in which a particular solute's retained by a column by virtue of a specific interaction w/a molecule covalently bound to stationary phase |
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| Volume Flow Rate |
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| volume of mobile phase per unit time eluted from the column |
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| Linear Flow Rate |
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| the distance per unit time traveled by the mobile phase |
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| Chromatogram |
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| graph showing chromatography detector response as a fxn. of elution time or volume |
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| Retention Time |
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| the time, measured from injection, needed for a solute to be eluted from a chromatography column |
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| Retention Volume |
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| the volume of solvent needed to elute a solute from a chromatography column |
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| Adjusted Retention Time |
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| the additional time required for a solute to travel the length of the column beyond the time required for unretained solvent |
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| Relative Retention |
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| ratio of adjusted retention times for 2 components |
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| Capacity/Retention Factor |
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| adjusted retention time for a peak divided by the time for the mobile phase to travel through the column |
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| Partition Coefficient |
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| equilibrium constant for rxn. in which solute's partitioned b/w 2 phases |
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| Resolution |
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| how close 2 bands in a spectrum/chromatogram can be to each other and still be seen as 2 peaks, and diff. in retention times of adjacent peaks divided by their width in chromatography |
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| Diffusion |
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| net transport of solute from region of high to low concentration caused by random movement of molecules in a liquid or gas |
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| Diffusion Coefficient |
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| the rate at which a substance moves randomly from region of high to lower concentration |
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| Plate Height |
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| length of chromatography column divided by number of theoretical plates in column |
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| Separation Factor/Relative Retention |
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| quotient of linear velocities of 2 solutes |
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| van Deemter Equation |
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| describes dependence of chromatographic plate height on linear flow rate |
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| Longitudinal Diffusion |
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| diffusion of solute molecules parallel to direction of travel through chromatography column |
