Unit 7: Solutions (Stillwagon)

intermolecular forces

intermolecular forces

- forces of attraction between molecules
- caused by polarity and movement of e- within bond

what is the fundamental difference between states of matter?

strength of imfs

London Dispersion Forces (LDF)

- a temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make them form dipoles
can be affected by:
1. # of e- (more e- = more ldf)
2. size/weight of the particles
3. shape of molecules (more compact = less ldf)

dipole-dipole forces (dp dp)

attractions between oppositely charged regions of polar molecules

hydrogen bond

- attraction between a slightly positive hydrogen atom and electronegative N, O, or F of other molecule
- require higher temp for boiling/melting

ion-dipole forces

attractive forces between an ion and a polar molecule (usually water)

melting/boiling points

- more imfs mean more energy required for state change
- more mass = stronger df

viscosity

- resistance of liquid to flow
- increases with stronger imfs, decreases with higher temp

Hydration

solvation with water as the solvent

Factors affecting rate of solvation

- stirring (makes H20 tear solutions apart)
- temp (higher temp = more collisions, causes increase of contact between solute and solvent)
- particle size (decrease particle size, increase surface area & contact)

saturation

Deals with number of particles dissolved in a solvent at a given temp
- saturated (max amount of solute)
- unsaturated (less than theoretically possible)
- supersaturated (more than theoretically possible)

which salt is the most soluble in water at 10c

potassium iodide