1. Ions in aqueous solutions and Colligative properties Chapter 14.1

2. Objectives Write equations for the dissolution of soluble ionic compounds in water. Predict whether a precipitate will form when solutions of soluble ionic compounds are combined, and write net ionic equations for precipitation reactions Compare dissociation of ionic compounds with ionization of molecular compounds Draw the structure of the hydronium ion, and explain why it is used to represent the hydrogen ion in solution Distinguish between strong electrolytes and weak electrolytes

5. Precipitation Reactions Solubility Guidelines ( Table pg. 900 in text) Most sodium, potassium, and ammonium compounds are soluble in water. Mostnitrates, acetates, andchloratesare soluble. Most chlorides are soluble, except those silver, mercury(I), and lead. Lead(II) chloride is soluble in hot water. Most sulfates are soluble, except those of barium, strontium, and lead. Most carbonates, phosphates, and silicates are insoluble, except those of sodium potassium, andammonium. Most sulfides are insoluble, except those of calcium, strontium, sodium, potassium, andammonium.

6. Will a precipitate form? (NH4)2S (s) 2 NH4+ (aq) + S2- (aq) Cd(NO3)2 (s) Cd2+ (aq) + 2 NO3- (aq) (NH4)2S (aq) + Cd(NO3)2 (aq) 2 NH4NO3 (aq) + CdS (s) Double Replacement Reaction Precipitate : Sulfides usually insoluble

7. Net ionic equations Includes only those compounds and ions that undergo a chemical change in a reaction in an aqueous solution. 2 NH4+(aq)+S2- (aq) + Cd2+(aq)+ 2 NO3-(aq) 2 NH4+ (aq)+2 NO3 -(aq) + CdS(s) Overall Ionic equation Spectator ions : Ions that do not take part in reaction They are found in solution before and after reaction Now , you have the Net Ionic Equation: Cd2+(aq)+ S2-(aq) CdS(s)

8. Ionization Ions are formed from solute molecules by the action of the solvent in a process Different than dissociation Molecular compounds form ions where there were none before HCl H+ (aq) + Cl- (aq) Hydronium ion H3O+ H2O(l) + HCl(g) H3O+(aq) + Cl-(aq)

9. Strong and Weak Electrolytes Strong electrolyte Any compound whose dilute aqueous solutions conduct electricity well; this is due to the presence of all or almost all of the dissolved compound in the form of ions. HCl, HBr, and HI completely ionize in water. H2O(l) + HCl(g) H3O+(aq) + Cl-(aq) Weak electrolyte Any compound whose dilute aqueous solutions conduct electricity poorly; this is due to the presence of a small amount of the dissolved compound in the form of ions. HF(aq) + H2O(l) H3O+(aq) + F-(aq)