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Chapter #14

Chapter #14. Ions in Aqueous Solutions and Colligative Properties. Chapter 14.1. Dissociation is the separation of ions that occurs when an ionic compound dissolves. NaCl Na + + Cl -. H 2 O. Na+. Na+. General Solubility Guidelines pg 427.

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Chapter #14

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  1. Chapter #14 Ions in Aqueous Solutions and Colligative Properties

  2. Chapter 14.1 • Dissociation is the separation of ions that occurs when an ionic compound dissolves. • NaCl Na+ + Cl- H2O Na+ Na+

  3. General Solubility Guidelines pg 427 • Most sodium, potassium, and ammonia compounds are soluble in water. • Most nitrates, acetates, and chlorates are soluble. • Most chlorides are soluble, except those of 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, and ammonium. • Most sulfides are insoluble, except those of calcium, strontium, sodium, potassium, and ammonium.

  4. H2O Will a precipitate form when ammonium sulfate and cadmium nitrate combine?? • Write the dissociation for each compound (NH4)2S 2 NH4+ + S2- Cd(NO3)2 Cd2+ + 2NO3- • Check the Solubility Guidelines to make sure they will dissociated. • Write the double replacement reaction if they are both soluble. (NH4)2S + Cd(NO3)2 (NH4)2(NO3)+ CdS • Check both products solubility on the chart…CdS is insolubleso it is the precipitate…. H2O

  5. Net ionic equation includes only those compounds and ions that undergo a chemical change in a reaction in an aqueous solution. (Not spectator ions) • Spectator ions are ions that didn’t take part in a chemical reactions. They are found on both sides of the reaction. Cd2+ + 2NO3- + 2NH4+ + S2- CdS + 2NO3- +2NH4+ Spectator Ions NO3- and NH4+ Cd2+ + 2NO3- + 2NH4+ + S2- CdS + 2NO3- +2NH4+ Net Ionic equation Cd2+ + S2- CdS

  6. Ionization is when ions are from solute molecules by the action of the solvent. In general mean the term is the creation of ions where there were none. • Ionization is different from dissociation. • Ionization happens with covalent (molecular) compounds and dissociation happens with ionic compounds. • Hydronium ion H+ or H3O+

  7. Strong electrolytes are any compound of which all or almost all of the dissolved compound exists as ions in an aqueous solution. (most acids and all ionic compounds) • Weak electrolytes is a compound of which a relatively small amount of dissolved compoud exist as ions in an aqueous. (covalent compounds)

  8. Chapter 14.2 Colligative properties are those that depend on the concentration of particles in a solution, not upon the identity of those properties. • Boiling Point Elevation • Freezing Point Depression • Osmotic Pressure

  9. Freezing Point Depression tf = kfm • Each mole of solute particles lowers the freezing point of 1 kilogram of water by 1.86 *C. • Kf = constant table 14-2 • m=molal moles/kg • tf= change in temp • That is why we salt the roads!!!!

  10. Boiling PointElevation tb = kbm • Each mole of nonvolatile solute particles raises the boiling point of 1 kilogram of water by 0.51 *C. • Kb =constant • m= molal • tf= change in temp

  11. Osmotic pressure is the external pressure that must be applied to stop osmosis. • Osmosis is the movement of solvent through a semipermeable membrane from the side of lower solute concentration to the side of higher solute concentration. • Semipermeable allow the movement of some particles while blocking the movement of others.

  12. “Dissociation”. April 23, 2007. http://www.biologycorner.com/resources/dissociation.gif • “Test Tubes”. April 23, 2007. http://www.myersconsultingservices.net/beaker_rainbow_close.jpg

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