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CHAPTER 14

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

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CHAPTER 14

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  1. CHAPTER 14 Ionic Compounds and Solution Formation

  2. 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”

  3. Dissolving Ionic Compounds • Charged ends of water (a dipole) attract ions and cause dissolving • http://www.mpcfaculty.net/mark_bishop/NaCl_dissolves.htm • Hydration • Dissolving with H2O as the solvent • Hydrate • Compound with trapped H2O in its crystal lattice • Copper (II) Sulfate Pentahydrate

  4. 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 =

  5. Dissociation Equations and Concentrations • Examples

  6. 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

  7. 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, Hg2+2 5. Carbonates, Hydroxides, Oxides, Sulfides, Phosphates, Oxalates are INSOLUBLE • Predict, write, balance double displacement reactions • Example • Potassium chloride + Silver (I) nitrate 

  8. 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

  9. Net Ionic Equations • Examples • Potassium chloride + Silver (I) nitrate 

  10. Potassium sulfate + Barium nitrate

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

  12. 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 • H2O + H+ -> H3O+

  13. 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!!

  14. Properties of Electrolytes • Conductivity • Strong electrolytes are more conductive (breaks apart into more ions!) • Water • Water does have ions! • Tap water vs. dH2O • Colligative Properties • BP elevation and FP depression  depend on solute concentration!!

  15. 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(NO3)2 is dissolved in 1.00kg of water?

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

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