1. Ch 13 Ions in Aq Soln and Colligative Properties 13
Ch 13 Ions in Aq Soln and Colligative Properties 13.1 Compounds in Aq Solns
Dissociation: separation of ions when it dissolves
Use the coefficients on the balanced eqn
NaCl (s)  Na + (aq) + Cl – (aq)

3. Precipitation Rxns Figure 1.3 (pg 413)
Not all ionic compounds are soluble in water
Ionic compounds with very low solubility are insoluble
Use basic rules to predict solubility
Ex: soluable NaNO3 K3PO4 (NH4)2S insoluable HgCl BaSO4

4. Net Ionic Eqns
Only compounds that undergo chemical change, removes spectator ions
Spectator ions not involved in chemical reaction
Example pg 416

5. Ionization: solute dissolved in solvent that forms ions
When molecular compounds form ions in soln
These molecular compounds tend to be polar
Not same as dissociation bc there were already ions present in dissociation reaction
Ionization makes ions from previously neutral
Hydronium Ion: H+ ion forms H3O+ ion
When molecular compounds ionize they release H+
H+ ions attracts other ions/molecules so strongly it doesn’t typically exist alone

6. An electrolyte’s strength depends on how many dissolved ions it has!
Strong Electrolytes: conduct electricity well, all/most dissolved compound is ions
HF(aq) + H2O(l) ↔ H3O+(aq) + F-(aq)
Weak Electrolytes: conduct electricity poorly, small amount dissolved compound is ions
CH3COOH(aq) + H2O(l) ↔ CH3COO-(aq) + H3O+(aq)

7. 13.2 Colligative Properties of Solutions
Recall: colligative properties depend on concentration of solute particles
Lowering vapor pressure depends on nonelectrolyte solute concentration
Nonvolatile substance is unlikely to become a gas under current conditions
2.1 pg 422

8. Solutions with nonelectrolyte solute will have:
Lowered freezing points
Molal Freezing-point constant: Kf
Freezing point depression: Δtf = Kfm
*Just change in temp subtract from normal freezing pt
Higher boiling points
Molal boiling-point constant: Kb
Boiling point depression: Δtb = Kbm
*Just change in temp ADD to normal boiling point!

9. Freezing point depression prob 425-426
“Steps”
Convert g to mol
Calculate molality
Write net ionic equn
Calculate molality of solution for # moles ions
Substitute values into formula (freezing/melting)
Freezing point depression prob

12. Recall: Osmosis is the movement from high to lower concentration of solute
Osmotic Pressure
Determined by concentration of dissolved solute
Pressure that must be added to stop osmosis (movement through membranes)
Semipermeable membrane: allows passage of some particles and blocks other particles

13. Total molality Determines changes in colligative properties
Calculated values are only expected values, actual values may be different because of how ions behave
PD 3 STOPED HERE