CHAPTER 14 Ionic Compounds and Solution Formation

Ionic Compounds in Solution Soluble in polar (dipole) solvent only! Solid ionics have equal totals of positive and negative charges Solid ionics have a crystal lattice structure In solution, ions separate and are free to move around –This is why solutions of ionic substances can conduct electricity (Video in AP Chemistry, Power Points folder, “Salt Water Conductivity”

Dissolving Ionic Compounds Charged ends of water (a dipole) attract ions and cause dissolving ssolves.htmhttp:// ssolves.htm Hydration –Dissolving with H 2 O as the solvent Hydrate –Compound with trapped H 2 O in its crystal lattice –Copper (II) Sulfate Pentahydrate

Heat of Solution Based on bond changes (last chapter!!) –Solute-solute bonds break Endothermic –Solvent-solvent bonds break Endothermic –Solvent-solute bonds form Exothermic Endothermic overall = Exothermic overall =

Dissociation Equations and Concentrations Examples

Solubility Equilibria Ionic compounds have different solubilities Compounds that are very slightly soluble form an equilibrium between solid compound and the ions –Example AgOH (s)Ag + (aq) + OH - (aq) -There would not be very many of the ions, but there would be some -Example: ppt will dissolve until no more can dissolve –Precipitation Reactions Solid (precipitate) formed when 2 ionic solutions are mixed

Solubility Rules Be able to use the solubility rules again!! Will be given on the test!! Solubility Rules 1. Group 1 and Ammonium compounds ARE soluble 2. Acetate, Nitrate, and chlorate compounds ARE soluble 3. Group 17 (other than F) ARE soluble EXCEPT when with Ag, Hg2+2, and Pb 4. Sulfates ARE soluble EXCEPT when with Ba, Sr, Pb, Ca, Ag, Hg Carbonates, Hydroxides, Oxides, Sulfides, Phosphates, Oxalates are INSOLUBLE Predict, write, balance double displacement reactions –Example Potassium chloride + Silver (I) nitrate 

Net Ionic Equations Shows only the compounds and ions that undergo a change Spectator Ions –There before and after – unchanged during a reaction –“watch” reaction Writing Net Ionic Equations –Write all aqueous (soluble) compounds as ions. Leave insoluble compounds as the full compound. –Cancel out spectator ions –Write “new” equation = NET IONIC EQN

Net Ionic Equations Examples –Potassium chloride + Silver (I) nitrate 

Potassium sulfate + Barium nitrate

Short cut: Potassium chloride + Lead (II) nitrate  Another question…What if they’re all aq??

Molecular Electrolytes Some molecular compounds can conduct electricity when dissolved. –Example HCl  H + (aq) + Cl - (aq) Ionization –Formation of ions because of action of solvent – happens usually with acids and bases Hydronium –Seen when an acid is placed in water –H 2 O + H + -> H 3 O +

Electrolytes Strong electrolyte –Ionizes almost completely Weak electrolyte –Gives low concentration of ions in aqueous solution –DOES NOT INDICATE DANGER VALUE!! It is a measure of ability to ionize only!!

Properties of Electrolytes Conductivity –Strong electrolytes are more conductive (breaks apart into more ions!) Water –Water does have ions! –Tap water vs. dH 2 O Colligative Properties –BP elevation and FP depression  depend on solute concentration!!

Colligative Properties Electrolytes affect colligative properties more than nonelectrolytes!! Need to calculate molality based on numbers of particles formed!! Example: What is the expected change in FP of water if 62.5g Ba(NO 3 ) 2 is dissolved in 1.00kg of water?

More practice What is the anticipated change in freezing point if 2.0mol NaCl is dissolved in 1.0kg water?