Determining the Buffering Capacity of Buffer

pH and Buffers

Determining the Buffering Capacity of Buffer #6

Introduction

A buffer is a solution that maintains pH for a system. (Promega Connections) A good buffer should have a component that acts as a base and a component that acts as an acid. (Symbiosis) It is able to neutralize small amounts of added acid or base, thus maintaining the pH of the solution relatively stable. This is important for processes and/or reactions which require specific and stable pH ranges. Buffer solutions have a working pH range and capacity which dictate how much acid/base can be neutralized before pH changes, and the amount by which it will change. (Chemwiki) The purpose of the lab experiment is to determine the buffering capacity of buffer #6. If I add more than 5 mL of an acid or base to buffer #6, it will reach its capacity.

Materials and Methods

I tested the pH of the solution buffer #6. Then I added 1 mL of sodium hydroxide to 120 mL of buffer #6. I added one more mL five more times, using a pH meter to record the new pH each time. I then repeated the entire process with hydrochloric acid.

Results

Amount of NaOH (sodium hydroxide) added

pH

0

6.21

1

7.17

2

10.49

3

11.26

4

11.54

5

11.65

6

11.74

Amount of HCl (hydrochloric acid) added

pH

0

6.18

1

5.37

2

4.92

3

4.47

4

4.07

5

3.47

6

2.83

After adding 2 mL of NaOH to buffer #6, the pH increased by a large amount. However, when adding more NaOH, the