Determining Ka of Weak Acid

Watch:

Complete: Lab Report below (attach your graphs)

At one-half the equivalence point of an acid base titration, the pH is equal to the ______.

What indicator is being used in this titration? ___________________

What pH do we expect at the equivalence point of this titration of a weak acid and strong base?

Acidic

Basic

Neutral

The shape of a titration curve ,since based on the logarithmic scale, best resembles which letter?

S

L

U

I

Data:

TRIAL 1

TRIAL 2

mL NaOH

pH

mL NaOH

pH

0

3.08

0

3.10

0.50

3.35

0.6

3.37

2.4

3.80

2.8

3.82

3.7

4.00

3.6

4.05

4.4

4.05

4.3

4.10

5.8

4.20

5.4

4.25

7.3

4.28

7.1

4.32

8.9

4.39

8.6

4.44

10.7

4.49

10.2

4.52

12.8

4.62

12.6

4.66

14.6

4.72

15.0

4.75

15.8

4.78

16.0

4.85

17.4

4.88

17.7

4.91

19.9

5.05

20.1

5.08

20.9

5.15

21.4

5.20

22.4

5.31

22.0

5.33

23.7

5.50

23.8

5.52

24.4

5.65

24.5

5.68

24.7

5.75

24.9

5.80

25.1

6.00

25.5

6.12

25.8

6.30

26.0

6.35

26.0

6.75

26.3

7.80

26.2

7.45

26.3

7.49

26.3

8.85

26.5

8.90

27.0

10.40

27.0

10.44

27.3

10.55

27.3

10.61

28.2

10.85

28.5

10.88

29.9

10.95

30.0

11.00

30.1

11.05

30.2

11.10

31.5

11.15

32.6

11.20

32.7

11.24

32.9

11.35

Graph each set of data!

Indicate how you arrived at the volumes you entered below by indicating the volume Volume @ Equivalence Point and Volume @ ½ Equivalence Point on our graphs (draw dotted lines, use color, etc).

Complete the table (show calculations below it):

Determined from Graphs

Trial 1

Trial 2

Volume @ Equivalence Point

Volume @ ½ Equivalence Point

pKa

Ka

Average Ka for both trials

Calculations

Trial 1 Ka:

Trial 2 Ka:

Average Ka: