1. And Strong Acid Weak Base
Weak Acid-Strong Base
And Strong Acid Weak Base

2. Objectives
Measure the molarity and Ka of a weak acid and identify what the acid is from Ka
Measure the molarity and Kb of a weak base and identify what the base is from Kb

3. Titration Curve
Ka can be determined if the titration curve has been measured
A titration curve is obtained when an acid is titrated with a base, and the pH of the resulting solution graphed as a function of the amount of titrant added via the burette
The equivalent point (where the acid is completely neutralized by the base) occurs at the center of the characteristic S curve
A Titration curve can be used to measure Ka of a weak acid or base

4. Measuring pKa of a weak acid
CH3COOH(aq) + NaOH(aq)  NaCH3COO(aq) + H2O(l)
here

5. Today Groups involve up to 4 people
Standardized NaOH
Today
Groups involve up to 4 people
Titrate 2O.00 mL of your unknown acid with the standardized NaOH
Phenolphthalein indicator (2 trials)
Equivalence point (just before the solution turns permanently pink
One titration curve per group
Calibrate with two buffer solutions
Determine Ka and identify the unknown acid
20.00 mL of your acid / 20 mL of deionized H2O
Magnetic stirrer
5 drops phenolphthalein

6. 2day or 2morrow pKb of a base
Standardized HCl
2day or 2morrow
pKb of a base
Titrate 20 mL of unknown base with standardized HCl
20.00 mL of your base / 20 mL of deionized H2O
Magnetic stirrer
5 drops phenolphthalein

7. Titration Curve