Chem 1120 1st Edition Lecture 18 Outline of Last Lecture I Weak Acid Strong Base Titration a 4 Regions II Diprotic Acids Types of Acid and Base Titrations III 4 pH Graphs Question IV Indicators Outline of Current Lecture I Solubility Equilibria II 4 Factors Affecting Solubility a Common Ion Effect b pH c Presence of Complexing Agents d Amphoterism III Precipitation and Separation of Ions Current Lecture I Insoluble Salts are often slightly soluble These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute PbF2 breaks into its ions somewhat and is not totally insoluble for example Ksp the solubility product is equal to the product of the concentration of the Pb2 ion and the concentration of the F ion squared solids omitted Solubility grams of solute dissolved in one liter of saturated solution Molar Solubility moles of solute dissolved in one liter of saturated solution Saturated Solution the max solute concentration at equilibrium Q rxn quotient Ksp Unsaturated Solution less than the max solute concentration at equilibrium Q Ksp Supersaturated Solution greater than max equilibrium solute concentration Q Ksp Example What s the solubility of PbF2 if the Ksp 4 1X10 8 II a Common Ion Effect If one of the ions in a solution equilibrium is already dissolved in the solution the equilibrium will shift to the left and the solubility of the salt will decrease For example Increasing the concentration of F in the previous solution will decrease solubility of PbF2 Example What s the solubility of PbF2 in 0 1 M NaF Ksp 4 1X10 8 b pH and solubility Example How does decreasing the pH affect the solubility of Cu OH 2 salt c Complex ion a species containing a central metal ion Lewis Acid bonded to one or more molecules or ions Lewis Base Formation of complex ions can increase the solubility of salts Example Calculate the molar solubility of AgCl in a 0 1 M NH3 solution given the Ksp of AgI and the Kf of Ag NH3 2 d amphoteric referring to a substance that will react with both an acid and a base Amphoteric metal oxides and hydroxides are soluble in strong acid or base because they can act either as acids or bases Examples Al3 Zn2 Sn2 Qualitative Analysis goal determine what is in a sample Quantitative Analysis goal determine how much is in a sample Years ago qualitative analysis employed mainly wet chemistry methods The analysis consisted of separation and confirmation and most separations were based on solubility differences These have been replaced by instrumental methods Selective Precipitation of Ions one can use differences in solubilities to separate the ions in a mixture
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