Chem 102 1st Edition Lecture 10 Outline of Last Lecture I. Relationship Between Ka and KbII. Acid-Base Properties of Salt SolutionsA. StructureIII. Lewis Acids and BaseOutline of Current LectureI. Buffered SolutionA. Composition and ActionB. Capacity and pHC. Addition of Strong Acids or BasesII. Strong Acid- Base TitrationCurrent LectureI. Buffered SolutionA. Composition and Action-A buffer consists of a weak acid and a conjugate base. A buffer resists a change in pH when a small amount of OH- or H+ is added. -When OH- is added to the buffer, the OH reacts with the HX to produce X- and water. But the HX/X ratio remains more or less constant, so pH barely changes. -When H+ is added to the buffer, X- is consumed to produce HX. Once again the HX/X ratio stays constant, so pH does not change much. B. Buffer Capacity and pH-Buffer capacity is the amount of acid or base neutralized by the buffer before there is a significant change in pH. This depends on the composition of the buffer. The greater the amounts of the conjugate acid-base pair , the greater the buffer capacity. The pH of the buffer depends on Ka. C. Addition of Strong Acids or Bases- We break calculations into two parts, stoichiometry and equilibrium. By knowing how much H+ or OH- was added to the neutralization reaction we know how much HX or X- is formed. With the concentrations of HX and X- we can calculate the pH from the Henderson-Hasselbalch equation: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.acid conjugatebase conjugatelogppH[HX]]X[logppH-aaKKII. Strong Acid-Base Titration-The equivalence point in titration is the point at which the acid and base are present in stoichiometric quantities. The end point of titration is the observed point. The difference between the equivalent point and end point is called titration error. The shape of a strong base-strong acid titration curve is very similar to a strong acid-strong base curve. -Initially, the strong base is in excess so the pH>7 as acid is added pH decreases but is still greater than 7. At equivalence point the pH is given by the strong acid in excess, so less than
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