Strong Electrolytes ( 100% ionized) A. Strong Acids: HCl, HBr, HI, H2SO4, HNO3, HClO4, HClO3 B. Strong Bases: Hydroxides of group IA and II A, Except Be and Mg C. Soluble Salts ( ionic compounds: metal/nonmetal) Always Soluble if these are in a compound Except with NO3-, Group IA, NH4+, CH3COO-, ClO4-, ClO3- No Exceptions Cl- Br-, I- Pb, Ag, Hg22+ SO42- Ag, Pb, Hg22+ Ca, Sr, Ba Mullis 1 Concentration Measurements Molarity = M = molality = m = moles of solute volume of solution in L moles of solute mass of solvent in kg Mole = X = moles of substance S Fraction total moles in solution Mullis 2 Colligative properties van’t Hoff factor = i i = number of ions one unit of substance will dissociate into in solution CaCl2 dissociates into Ca2+, Cl- and Cl-, so i= 3. Boiling Point Elevation ΔT = ikbm ΔT = increase in solution boiling point kb = boiling point elevation constant for the solvent m = molality Mullis (for now) 3 Freezing Point Depression ΔT = ikfm ΔT = decrease in solution freezing point kf = freezing point depression constant for the solvent m = molality Vapor Pressure Lowering P = XPº P = vapor pressure of the solution X = mole fraction of the solvent Pº = vapor pressure of the pure solvent Add solute: Solution’s vapor pressure goes down. Lower vapor pressure = Raise boiling point Mullis 4 Solubility Product For the reaction: AaBb(s) a Ab+(aq) + b Ba-(aq) The solubility expression is: Ksp = [Ab+]a[Ba-]b Example: The solubility of strontium fluoride in water is 1 x 10-3 M at room temp. What is the value of its solubility product? [Sr2+] = 1 x 10-3 M and [F-] = 2 x 10-3 M SrF2 Sr2+ + 2F- so Ksp = [Sr2+][F-]2 Ksp = [1 x 10-3 M][2 x 10-3 M]2 = 4 x 10-9 Mullis 5 Intermolecular forces: Generalizing properties Low boiling point = particles are more likely to leave liquid solution Weaker IM forces = lower boiling point Lower boiling point = more vapor = higher vapor pressure High boiling point = slow evaporation If IM forces are the same, look at formula weight. Heavier molecules have higher boiling points. Strength of IM forces: Hydrogen bond>dipole-dipole>London dispersion Mullis 6 Intermolecular Forces (Chart from Chemistry: The Central Science by Brown-LeMay et al.) Interacting molecules or ions Polar molecules? No Ions involved? Yes Are polar molecules and ions both present? Yes No Are H atoms bonded to N,O or F atoms? No London Forces only Ex. Ar(l), I2(s) Dipole-Dipole Ex. H2S Yes No Yes Hydrogen Bonding Ex. NH3, H2O Mullis Ion-dipole Forces Ex. KBr in H2O Ionic bonding Ex. NaCl 7