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
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