Ch 13 Ions in Aq Solns and Colligative

Ch 13 Ions in Aq Solns and Colligative Properties 13. 1 Compounds in Aqueous Solutions • Dissociation: separation of ions when it dissolves – Use the coefficients on the balanced eqn • Precipitation Rxns – Figure 1. 3 (pg 413) • Net Ionic Eqns – Only compounds that undergo chemical change, removes spectator ions

• Ionization: solute dissolved in solvent that forms ions • Hydronium Ion: H+ ion forms H 3 O+ ion • An electrolyte’s strength depends on how many dissolved ions it has! – Strong Electrolytes: conduct electricity well, all/most dissolved compound is ions – Weak Electrolytes: conduct electricity poorly, small amount dissolved compound is ions

13. 2 Colligative Properties of Solution • Lowering vapor pressure depends on nonelectrolyte solute concentration • 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!

• Osmotic Pressure – Determined by concentration of dissolved solute – Pressure that must be added to stop osmosis (movement through membranes) • Total molality – Determines changes in colligative properties – Calculated values are only expected values, actual values may be different because of how ions behave