Why you should understand Buffers:
Buffers are essential for life. Many systems rely on buffers, like blood and soaps. Without buffers, life wouldn't be possible.
Key Concepts
- Defining a Buffer
- pKa and Buffers
- Making a Buffer
- Example
Defining a Buffer
A buffer is a solution that resists changes in pH. A buffer is a solution that contains both a weak acid and a conjugate base pair. Buffers are very important to biological systems such as blood pH. A buffer maintains the pH of our blood which keeps us alive. If the pH of our blood changed by even one or two pH numbers, we would be dead.
pKa and Buffers
Buffers have what is called a "Buffering Capacity". Buffering Capacity is a measure of the effectiveness of a buffer. The pH where a buffer is most useful or has the most buffering capacity is specific to the conjugate acid-base pair. This pH is plus or minus one unit of the pKa of the weak acid in the buffer.
When choosing a buffer system, you typically pick a weak acid based on its pKa and the desired pH of the system.
Making a Buffer
Below, I lay out the method for making a buffer.
After solving for the ratio of conjugate acid to base, dimensional analysis can be used to determine the amount of conjugate base and acid that need to be added to the solution. The actual pH of the buffer can then be measured. At that point, you've successfully created a buffer.
Example
Below I've given an example problem for you to practice with. I solve this problem in my youtube video on buffers (attached below). I will also be writing an explanation of how to solve this problem, directly below the example.
Answer:
This example problem asks us to create a buffer with a pH of five. We are limited to the acids listed in the problem. The rule for choosing acids for a buffer system is that the pKa of the acid needs to be within one unit of the desired pH. This means that the pKa can be between 4 and 7. The only acid in the problem which fits this criterion is acetic acid. The conjugate base of acetic acid is the acetate ion.
Summary
- A buffer is a solution that resists changes in pH. A buffer is a solution that contains both a weak acid and a conjugate base pair.
- The pH where a buffer has the most buffering capacity within plus or minus one unit of the pKa of the weak acid in the buffer.
I hope you've found this post helpful. Please leave a comment or message me if you have any questions. I've also attached my Youtube video about buffers below.
- Saren
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