CH 220: FINAL EXAM

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CH 220
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intermolecular forces
attraction b/w molecules
intramolecular forces
attractions within a molecule
dipole-dipole forces
attraction b/w polar molecules
London dispersion forces
attractive forces caused by temporary or induced dipoles
volatility
tendency of a substance to become a gas
hydrogen bonding
IM attraction b/w H & O, N, or F; polar bond
viscosity
resistance to flow
surface tension
amt of work necessary to extend a liquid's surface
steam
water molecules above boiling pt
vapor
water molecules below boiling pt
boiling point
point where vapor pressure exeeds atmospheric pressure
normal boiling pt
boiling pt of a liquid at 1 atm (100° C H2O)
enthalpy of vaporization (ΔHvap)
energy needed to vaporize 1 mole of a liquid at 1 atm
phase change
transformation of one physical state to another
endothermic
energy put into a system (heating)
exothermic
energy released from a system (cooling)
sublimination
heating solid->gas
deposition
cooling gas->solid
enthalpy of fusion (ΔHfus)
energy needed to melt 1 mole of a solid
triple point
all 3 phases in equilibrium
critical point
highest T & P where you can achieve a liquid
solution
homogenous mixture of 2 or more substances
strong electrolyte
breaks apart fully
colligative properties
solution properties that depend on the # of solute particles, not the solute identity
osmosis
flow of solvent through semi-permeable membrane to equilize concentrations
osmotic pressure
max opposing pressure required to prevent osmosis from occuring
electrolyte
substance dissolved in water to produce charged particles (ions)
Vant Hoff factor
(i); # particles produced by an electrolyte
acid
substance that produces H+ when dissolved in water
base
substance that produces OH- when dissolved in water
amphoteric
any species that can react as either an acid or a base
strong acid
dissociates completely
strong base
completely dissociates in water (alkali metal hydroxides NaOH & alkaline earth hydroxides Ca(OH)2)
buffer
solution that resists change in pH when additional acid or base is added; composed of acid/base + its conjugate
buffer capacity
# of moles of strong acid/base needed to cause a 1 pH change of a buffer
titration
controlled mixing of 2 reactive species; monitor some function of the reaction
acid-base titration
plot pH as a function of added titrant
equivalence point
moles of acid present is equal to the moles of base added
monoprotic
donates 1 proton in an acid-base reaction
polyprotic acid
ability to donate more than 1 proton in an acid-base reaction (ex. amino acid)
ligand
atom or molecule capable of forming a covalent bond to a metal ion via an electron pair
complex ion
ion containing 2 or more ions or molecules that are stable themselves; ligand-metal combination
monodentate ligand
binds to a metal ion through only one site
chelate
ligand which binds a metal w/ at least 2 sites & forms a cyclic structure
EDTA
important chelating agent; 1:1 ratios
direct titrations
titrant added to metal ion solution until endpoint is reached & color change is observed
back titration
known excess of EDTA added to metal ion analyte; after reaction, remaining EDTA titrated with 2nd metal ion in a diff. reaction
indirect titration
EDTA titrant is used with and intermediary that has a known relationship w/ the analyte of interest
endpoint
point in titration at which there is a sudden change in a physical property (color, pH, conductivity, or absorbance); used as a measure of equivalence pt
solubility equilibria
equilibrium b/w solid & its dissolved constituents
solubility
max amt of solid that will dissolve in 1 L of pure water at 25°
saturated
when solution contains max amt of dissolved solution
Le Chatelier's Principle
If a system at equilibrium is disturbed, the direction in which it proceeds back to equilibrium is such that the disturbance is partly offset
gravimetric analysis
mass of a product determines quantity of analyte; dependent on precipitation
classical/wet chemical analysis
gravimetric & volumetric; tedious, slow, more accurate
volumetric analysis
volume of reagent needed to react with analytes determines amount of analyte
instrumental analysis
started w/ solid state electronics, fast, poor precision & accuracy
oxidation
loss of electrons; oxidation # increases
reduction
gain of electrons; oxidation # decreases
oxidation numbers
show how many electrons have been gained/lost by a neutral atom when it forms a compound
electrochemistry
studies relationship b/w chemical reactions & electricity
electrochemical cell
2 half cells; voltaic & electrolytic
voltaic cell
use chemical reactivity to generate electrical energy; spontaneous e- flow (i.e. battery); anode -, cathode +
electrolytic cell
use electrical energy to drive chemical reaction; not spontaneous (i.e. charger); anode +, cathode -
cathode
where reduction occurs
anode
where oxidation occurs
salt bridge
to preserve charger neutrality cations & anions move from a salt bridge to counterbalance moving e-
spectrophotometry
measurement of light intensity as a function of wavelength
polarized light
field oscillates in one plane
normal light
field oscillates in all directions
blank
contains all reagents except analyte, compensates for absorbance of pure solvent; generally subtract blank absorbance from all other absorbances before calculations
isosbestic point
wavelength where absorption spectra of 2 species cross each other; shows only 2 components present w/ a constant total concentration
accuracy
how close a measurement is to true value
precision
how well repeated measurements agree; reproducibility
systemic error
determinant error; bias, caused by incorrect procedure or faulty equipment; can be corrected
random error
indeterminant; resulting from intrinsic uncertainty of measurement; creates scatter in data; can be minimized but not corrected
confidence interval
range of values in which there is a specified probability that the "true" value will be found
calibration curves
plot of physical response against concentration

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