Question

 

Data Table 1. Adding 0.1 M HCl from D1 into A1.

Number of Drops	pH of Solution
0	6
2	6
4	6
6	6
8	6
10	6
12	6
14	6
16	6

Data Table 2. Adding 0.1 M NaOH from D6 into A6.

Drop Number	pH of Solution
0	6
2	6
4	6
6	6
8	6
10	6
12	6
14	6
16	6

Data Table 3. Adding 6 M HCl from Pipet into B1.

Drop Number	pH of Solution
0	6
2	6
4	4
6	2
8	2
10	2

Data Table 4. Adding 6 M NaOH from Pipet into B6.

Drop Number	pH of Solution
0	6
2	6
4	6
6	8
8	10
10	12

Data Table 5. Adding 0.1 M HCl from D1 into C1.

Drop Number	pH of Solution
0	6
2	4
4	4
6	4
8	4
10	4

Data Table 6. Adding 0.1 M NaOH from D6 into C6.

Drop Number	pH of Solution
0	6
2	12
4	12
6	12
8	12
10	12

1. Describe the buffer capacity of the acetic acid buffer solution in relation to the addition of both concentrated and dilute acids and bases. Reference the results in Data Tables 1-4 in your answer.

2. Did distilled water act as a buffer in this experiment? Use your data to support your answer.

Answer 1

1. From the data given above,

The buffer capacity of acetic acid was found to maintain its pH when either 0.1 M HCl (Table 1) or 0.1 M NaOH (Table 2) were added to the buffer solution. No change in the pH was observed in these cases.

When 6 M HCl (Table 3) or 6 M NaOH (Table 4) where added to the buffer solution, initially the pH of the buffer was well maintained upto volume 2 ml for HCl and 4 ml for NaOH at which point the buffer capacity for the buffer resisted any change in pH. After 4 ml of HCl or 6 ml of NaOH, we see a large difference in the pH of the solution. This is where the buffer capacity for the acetic acid buffer cease to exist. The pH of solution no longer remained constant.

2. Distilled water did not act as buffer in the experiment. It only reduced the buffer capacity of the acetic acid buffer solution by dilution effect. So more dilute the solution is more easily it reaches its buffer capacity by addition of acid or base.