Unit 3
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Three types of Intermolecular Forces
• Dipole-Dipole • H Bonds • London Dispersion
What are dipole dipole bonds and its properties?
polar molecule attraction melts and boils at low temps due to weak attraction - gases and liquids at room temps
What are H bonds and what are its properties?
When H gives up its e-, it has a + charge High boil and melt temps due to STRONG attraction (liquids)
Why are H bonds the strongest?
There is no electron shielding so the attraction is much much stronger
What are London Dispersion Forces
Depends on random motion of e-: higher number of e- = higher attraction = higher melting and boiling points (gases)
What is the weakest IMF?
London Dispersion Forces due to the randomness
What kind of molecule does not experience IMFs?
Ionic Molecules and they are SOLIDS at room temp
What happens to Ionic bonds when they change phases?
bonds are broken
What happens to covalent bonds when they change phases?
bonds are NOT broken
What are the melting point <> stuff
network covalent > ionic > metallic > covalent
Vapor Pressure
molecules are in constant motion. If they hit hard enough, they can escape from their IMF
if temperature rises, vapor pressure…
increases
if there are stronger IMF, vapor pressure
is weaker
What is the rule for dissolving?
Like dissolves like polar dissolves polar
Electrolytes
the ions dissolved from ionic bonds, which are great for electric conductivity
What does distillation do?
Takes advantage of different boiling points to separate mixtures of substances.
What does a Maxwell Boltzmann diagram tell me?
Demonstrates the range of velocities for the molecules of gas.
If temperature rises, Kinetic Energy…
increases
Effusion
rate of gas diffusing through microscopic holes
If temperature rises, rate of effusion…
increases
If mass of the individual gas is bigger, rate of effusion…
decreases
Ideal Gas Equation
PV = nRT
Combined Gas Law
(P1V1)/T1 = (P2V2)/T2
Boyle’s Law
P1V1 = P2V2