26 Cards in this Set
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Dipole-Dipole
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b/t polar molecules (permanent dipoles)
Strength increases with increasing magnitude of dipole
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Ion-Dipole
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b/t ions & polar compounds
VERY STRONG
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Hydrogen bonding
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'super' dipole-dipole
molecules containing H bonded with F, O, or N
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Dispersion
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b/t all molecules and atoms due to temporary dipoles
increase with increasing molecular/atomic polarizability
Polarizability increases with mass (# of e)
when molecules have similar mass, consider how shape impacts interaction
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viscosity
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the resistance of a liquid to flow
greater in substances with stronger IM forces
increasing in longer molecules that can interact over a greater area and possibly become entangled
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vaporization
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the phase transition from liquid to gas
increases with inc T and inc Surface area
decreases with increasing strength of IM forces
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Vapor pressure
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pressure of a gas in dynamic equilibrium with a liquid
normal boiling point- T where the vapor pressure of a gas equals 1 atm
Boiling point- T where vapor pressure of a gas equals the external pressure
water boils at a lower T at high elevation because atm is lower
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Pressure
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units- atm, Pa, mm Hg, torr
open end manometer: Pgas= Patm + delta h
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boyle's law
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P1V1=P2V2 (constant T and n)
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Charles' Law
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V1/T1=P2/T2 (constant P and n)
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Avogandro's law
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V1/n1=V2/n2 (constant P and T)
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combined gas law
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P1V1/T1= P2V2/T2
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Ideal gas law and applications
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PV=nRT
STP= 1 atm, 0C
Molar volume: 1 mole of an ideal gas @STP= 22.4L
Density of a gas: d=P*mm/RT (mm=molar mass)
determine molar mass of a gas given info on a sample mass, T, P and V
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Mixtures of Gases , Partial Pressures
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Ptot=PA+PB+PC... (dalton's Law of Partial Pressures)
PA= nART/V, PB=nBRT/V, PC= nCRT/V
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Mole Fraction
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XA = nA/ntot
PA = XA*Ptot
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Collecting gas over water
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Pgas = Ptot -- PH20
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Gases in chemical reactions (Stoichiometry)
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write a balanced chemical reaction involving gases (PVT of gas A ==> amount A (in moles) ==> amount B (in moles) ==> PVT of gas B)
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Kinetic Molecular Theory
Postulates
what real gasses do
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Postulates
gases molecules/atoms are in constant, straight line motion
V of gas particles in negligible compared to volume of container
IM forces b/t gas particles are negligible
collisions b/t particles and container walls are completely elastic
Avg KE of particles is proportional t…
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Kinetic Molecular Theory
Temperature and molecular velocities
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@ a given T, lighter particles travel faster (on avg) than heavier particles
As T inc, the velocity destribution of gas molecules shifts towards higher Ts and becomes less sharply peaked
for a gas sample: KEavg= 3/2 RT
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VSEPR Theory
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Repulsion of e groups determines molecular shape
Electron grps: single bonds, multiple bonds (double, triple), lone pairs of e, single lone e
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3 basic shapes and ideal bond angles
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linear- 180 degrees
trigonal planar- 120 degrees
tetrahedral- 109.5 degrees
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Effect of lone pairs of e and multiple bonds on ideal bond angles
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null
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Electron geometry vs. Molecular Geometry
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excel graph
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Predicting the shapes of larger molecules looking at central/internal atoms
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null
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Molecular shape and polarity
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dipoles are vector quantities
estimate net dipole to determine molecular polarity
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valence bond theory
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covalent bond rep'd by overlapping atomic orbitals
overlapping orbital may b standard atomic orbitals ( i.e. s, p) or hybridized atomic orbitals (i.e. sp, sp2, sp3)
hybrid orbitals
the # formed is = to # of atomic orbitals mixed
E is intermediate b/t those of the mixed atomic orbitals…
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CHM 103: POLYATOMIC IONS