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UNIT 11: SOLUTIONS & COLLOIDS
DISSOLUTION PROCESS
FORMATION OF SOLUTIONS:
- Solute-solute IMFs must be overcome ( ENDOTHERMIC )
- Solvent-solvent IMFs must be overcome ( ENDOTHERMIC )
- Solute-solvent attraction forces occur ( EXOTHERMIC )
The relative magnitudes of the energy changes associated w/ these stepwise processes
determine whether the dissolution process will release or absorb energy.
In some cases, solutions do not form b/c the energy required to separate solute and solvent
species is so much.
ELECTROLYTES
ELECTROLYTES NONELECTROLYTES
Substances that dissolve in water and produces ions
Substances that DO NOT produce ions when dissolved in water
STRONG : 100% of the dissolved substance generates ions
- Strong ACIDS: HCl, H2SO
- Strong BASES: NaOH, KOH
- Salts: BaCl, BaS
WEAK : small fraction of dissolved substances generates ions
- Weak ACIDS: HCN, CH 3 COO
- Weak BASES: NH3, CH 3 NH 2 H
Ex: H2O, CH 3 OH, C12H22O
SOLUBILITY OF AN IONIC COMPOUND
ION-DIPOLE ATTRACTION OPPOSITELY CHARGED IONS
If this dominates:
COMPOUND DISSOLVES
⬆ water solubility
If this dominates:
Compound DOES NOT DISSOLVE
⬇water solubility
SOLUBILITY
Solubility: The maximum concentration of a solute that can be achieved in a particular solvent under given conditions.
2 substances have similar IMFs = soluble in one another
Nonpolar solvents dissolve nonpolar
solutes
Polar solvents dissolve polar/ionic solutes
SATURATED UNSATURATED SUPERSATURATED
Solute [ ] = its solubility
ex: sugar added to coffee
- saturation point is reached when sugar stops dissolving
Solutes [ ] < its solubility
ex: salt water
- you can add more salt to water and it would still dissolve
Solutes [ ] > its solubility (at lower temperature)
ex: reusable hand warmers
- releases heat and crystallizes over time
Depends on several factors like:
- ⬆ TEMPERATURE = ⬆ SOLUBILITY
- PRESSURE (with a gaseous solute)
COLLIGATIVE PROPERTIES
Property of a solution that depends on the [ ] of the solute.
THE PROPERTIES:
MISCIBLE: 2 liquids that mix with each other
- ex: ethanal & water, gasoline & oil
IMMISCIBLE: 2 liquids that DO NOT mix
- ex: non-polar liquids (gasoline, oil, bromine) & water
