17.3b Weak Acid Strong Base Titrations pH Calculations | General Chemistry

Chad's Prep
Chad's Prep
49.1 هزار بار بازدید - 2 سال پیش - Chad provides a thorough lesson
Chad provides a thorough lesson on how to perform pH calculations for Weak Acid-Strong Base Titrations.  Reactions between weak acids and strong bases effectively go to completion, and therefore the reaction between them can be treated as a limiting reagent calculation.  Before the addition of strong base (the initial point on the titration curve) there is only weak acid in the solution and calculating the pH of a weak acid was presented in chapter 16.

Before the equivalence point in a weak acid-strong base titration the addition of strong base has neutralized some but not all of the weak acid converting it into its conjugate base.  Having both weak acid and conjugate base in the solution, the pH can be calculated using the Henderson-Hasselbalch equation.

At the equivalence point in a weak acid-strong base titration, effectively all of the weak acid has been converted into its conjugate base (which is a weak base), and calculating the pH of a weak base was presented in chapter 16.  The tricky part is that one will typically have to determine the value of Kb from the relation: KaKb = Kw.

Finally, after the equivalence point in a weak acid-strong base titration there will be excess strong base remaining in the solution along with the production of the conjugate base.  For practical purposes, the contribution of the weak base is ignored, and the pH of the solution is calculated as if it were simply the pH of a strong base solution.

The lesson is concluded by explaining weak base-strong acid titration curves and showing how weak base-strong acid pH calculations are analogous to weak acid-strong base pH calculations.

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00:00 Lesson Introduction
00:30 Weak Acid-Strong Base Titrations pH at Initial Point
04:25 Weak Acid-Strong Base Titrations pH Before Equivalence Pt
11:05 Weak Acid-Strong Base Titrations pH at Half-Equivalence Pt
14:47 Weak Acid-Strong Base Titrations pH at Equivalence Point
21:16 Weak Acid-Strong Base Titrations pH after Equivalence Pt
25:44 Weak Base-Strong Acid Titration Curve and pH Calculations

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2 سال پیش در تاریخ 1400/11/28 منتشر شده است.
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