Testing the buffering capacities of various solutions

Testing the buffering capacities of various solutions

1. Obtain and label four test tubes according to the four solutions listed in Table 2.

2. Place 5 ml of each solution into its appropriately labeled tube.

3. Measure the pH of each of the solutions in the tubes and record these initial values in Table 2.

4. Add 5 drops of acid (0.1 M HCl) to the first tube. Cover the tube with parafilm and invert the tube gently to mix the contents.

5. Measure the pH of the acidified solution and record it in Table 2.

6. Repeat steps 4 and 5 for each of the remaining tubes. Record your results in Table 2.

7. Compare the initial pH and the pH after acid addition for each sample.

Table 2: Buffering Capacity Data

Solutions	Initial pH	Final pH (after HCl)	Comparison of pHs
Water	5	2	PH dropped by 3
0.1 M NaCl	5	3	PH dropped by 2
Skim milk	6	5	PH dropped by 1
0.1 M phosphate buffer	7	7	PH stayed the same

Analysis Questions:

1. What is the biological importance of using a buffer?

Buffers prevent changes in PH, and maintain balance.

2. Which of the solutions is the most effective buffer? Least effective?

The most effective buffer is the solution who’s PH changed less, (in this case will be 0.1M phosphate buffer). The least effective solution will have a significant change in PH (in this case it will be H2O with an original PH of 5, and a final PH of 2 after addition of 0.1M of HCL)

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