Chem 1120 1st Edition Lecture 18Outline of Last Lecture I. Weak Acid-Strong Base Titrationa. 4 RegionsII. Diprotic Acids/Types of Acid and Base TitrationsIII.4 pH Graphs QuestionIV.IndicatorsOutline of Current Lecture I. Solubility EquilibriaII. 4 Factors Affecting Solubilitya. Common Ion Effectb. pHc. Presence of Complexing Agentsd. Amphoterism III. Precipitation and Separation of IonsCurrent LectureI. “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 thePb2+ ion and the concentration of the F- ion squared (solids omitted):Solubility = grams of solute dissolved in one liter of saturated solutionMolar Solubility = moles of solute dissolved in one liter of saturated solutionSaturated Solution ——> the max solute concentration at equilibrium, Q(rxn quotient) = KspUnsaturated Solution ——> less than the max solute concentration at equilib-riumQ < KspSupersaturated Solution ——> greater than max equilibrium solute concen-trationQ > KspExample: 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 al-ready 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^-8b) 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 saltsExample: 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 anda baseAmphoteric 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 sampleQuantitative Analysis = goal: determine how much is in a sample*Years ago qualitative analysis employed mainly “wet chemistry” methodsThe analysis consisted of separation and confirmation and most separations were based on solubility differences. These have been replaced by instru-mental methodsSelective Precipitation of Ions = one can use differences in solubilities to sep-arate the ions in a
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