Transcript 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. HO • NaCl Na+ + Cl2 Na+ Na+ General Solubility Guidelines pg 427 1. Most sodium, potassium, and ammonia compounds are soluble in water. 2. Most nitrates, acetates, and chlorates are soluble. 3. Most chlorides are soluble, except those of silver, mercury (I), and lead. Lead (II) chloride is soluble in hot water. 4. Most sulfates are soluble, except those of barium, strontium, and lead. 5. Most carbonates, phosphates, and silicates are insoluble, except those of sodium , potassium, and ammonium. 6. Most sulfides are insoluble, except those of calcium, strontium, sodium, potassium, and ammonium. Will a precipitate form when ammonium sulfate and cadmium nitrate combine?? 1. Write the dissociation for each compound (NH4)2S Cd(NO3)2 2. 3. H2O H2O 2 NH4+ + S2Cd2+ + 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 4. (NH4)2(NO3) + CdS Check both products solubility on the chart…CdS is insoluble so it is the precipitate…. • 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+ + S2CdS + 2NO3- +2NH4+ Spectator Ions NO3- and NH4+ Cd2+ + 2NO3- + 2NH4+ + S2CdS + 2NO3- +2NH4+ Net Ionic equation Cd2+ + S2CdS • 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+ • 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) 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 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!!!! Boiling Point Elevation 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 • 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. • “Dissociation”. April 23, 2007. http://www.biologycorner.com/resources/di ssociation.gif • “Test Tubes”. April 23, 2007. http://www.myersconsultingservices.net/be aker_rainbow_close.jpg