Chem 102 1st Edition Lecture 11 Outline of Last Lecture I. Buffered SolutionA. Composition and ActionB. Capacity and pHC. Addition of Strong Acids or BasesII. Strong Acid- Base TitrationOutline of Current LectureI. Weak Acid- Strong Base TitrationII. Titrations of Polyprotic AcidsIII. Solubility Equilibria Current LectureI. Weak Acid- Strong Base Titration-Consider the titration of acetic acid with NaOH. Before any base is added the solution contains only weak acid, so the pH is given by the equilibrium calculation. As the strong baseis added, the strong base consumes a stoichiometric quantity of a weak acid. The pH is givenby the buffer equation. At the equivalence point all the acetic acid and NaOH has been consumed. However a product has been generated, which gives off the pH. After the equivalence point, the pH is given by the strong base in excess. -For a strong acid-base titration, the pH begins at less than 7 and gradually increases as baseis added, near the equivalence point the pH increases dramatically. However, for a weak acid- strong base titration, the initial pH rise is more steep than the strong acid- strong base case, then there is a leveling off due to buffer effects. -The inflection point is not as steep for a weak acid- strong base titration. The shape of the 2curves after equivalence point is the same because pH is determined by the strong base in excess. The amount of initial rise in pH and the length of the inflection point at equivalence affect the titration curves. Weaker acid= smaller equivalence point inflection. 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.II. Titrations of Polyprotic Acids-In polyprotic acids, each ionizable proton dissociates in steps. In a titration, there are n equivalence points corresponding to each ionizable proton. III. Solubility Equilibria-The solubility product is the molar concentration of ions raised to their stoichiometric power. Solubility is the amount, in grams, of substance that dissolves to form a saturated solution. Molar solubility is the number of moles of solute dissolving to form a liter or saturated solution. -To convert solubility to Ksp, Solubility needs to be converted into molar solubility via molar mass. Molar solubility is then converted into the molar concentration of ions at equilibrium, Ksp is the product of equilibrium concentrations of
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