956 Words4 Pages

pKa of a Weak Acid
Introductory Chemistry 1120 pKa of a Weak Acid
1. A results section for the pKa lab. See the example results section from the chemical equilibrium experiment and the details of a results section on page xi of your lab manual.
On this table shows the volume of the titration. Unknown acid buret | | | | Trial #1 | Trial #2 | Initial buret reading | 20.5 mL | 21.8 mL | Final buret reading | 40.5 mL | 45.1 mL | Volume of acid added | 20.0 mL | 23.3 mL |
This second table shows the calculation of the pH at half equivalence point, average pKa and the average of the unknown acid.
The volume of equivalence point was found by picking the steepest portion of the curve or point of inflection from the graph; and tracing the point to the volume NaOH added. One-half the equivalence point was determined by dividing by ½ of the volume of equivalence point. Once the one-half of the equivalence point was found, trace the point until you hit the graph line and trace it to the pH-axis.
Results | | | | Trial #1 | Trial #2 | Volume of NaOH at equivalence point | 9.5 mL | 13.7 mL | Volume of NaOH at one-half the equivalence point | 4.75 mL | 6.9 mL | pH at half equivalence point | 5.42 | 5.3 | pKa of unknown acid | 5.42 | 5.3 | Average pKa | 5.36 | 5.36 | Average Ka | 4.4 * 10-6 | 4.4 * 10-6 | Moles of unknown acid | 1.30 * 10-3 moles | 1.87 * 10-3 moles | M of unknown acid | 0.0650 M | 0.0805 M | Average M of unknown acid | 0.07275 M | 0.07275 M |
2. The data table containing all your raw and manipulated data (like the one found on page 47 of your lab manual). Be sure to include your lab partner’s name and unknown number.
Unknown acid buret | | | | Trial #1 | Trial #2 | Initial buret reading | 20.5 mL | 21.8 mL | Final buret reading | 40.5 mL | 45.1 mL | Volume of acid added | 20.0

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