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July 7, 2015

Homework Help: chemistry

Posted by Kasen on Saturday, April 5, 2008 at 1:52pm.

Lab: Determining Ka of Acetic Acid

Purpose: The purpose of this experiment is to determine the molar concentration of a sample of acetic acid and to calculate its Ka.

Materials:
25 mL pipet and bulb burette 2x150 mL beaker
125 mL Erlenmeyer flask acetic acid solution sodium hydroxide solution
phenolphthalein pH metre

Procedure:
1. Record the molar concentration of the NaOH solution.
2. Produce a table to record your data. It should have one column for volume of NaOH added and one column for pH.
3. Obtain 50 mL of acetic acid and place it into a beaker.
4. Place 50.0 mL of NaOH into the burette.
5. Pipet 25.0 mL of acetic acid into the Erlenmeyer flask. Add two drops of phenolphthalein to the acid.
6. Record the initial pH of the solution.
7. Add 1.00 mL of NaOH from the burette to the Erlenmeyer until the pH reaches 5.00. Record the volume to two decimal places. Measure the pH of the solution each time you add NaOH.
8. Above pH=5.00, add NaOH in 0.10 or 0.20 mL portions. Record the volume at which the phenolphthalein turns pink.
9. Continue to add NaOH until the pH reaches 11.00. Above pH=11.00, add 0.10 mL portions until the pH reaches 12.00.
Note: All you actually have to do is start the burette running, the values will record as you progress through the lab.



NaOH(ml) pH
0.00 2.52
1.00 3.58
2.00 3.59
3.00 4.92
4.00 4.09
5.00 4.14
6.00 4.55
7.00 4.73
8.00 4.98
9.00 5.07
9.20 5.09
9.40 5.14
9.60 5.19
9.80 5.24
10.00 5.25
10.20 5.37
10.40 5.38
10.60 5.45
10.80 5.59
11.00 5.62
11.20 5.75
11.40 6.18
11.60 6.29
11.80 6.54
12.00 10.68
12.20 11.15
12.30 11.36
12.40 11.43
12.50 11.57
12.60 11.65
12.70 11.67
12.80 11.77
12.90 11.79
13.20 11.83
13.40 11.84
13.60 11.88
14.10 11.92
15.00 12.00

Analysis:
Write the chemical equation for the neutralization reaction you observed.

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