Buffer Lab Simulation
Buffers are solutions of a weak acid and it’s conjugate base that are able to resist changes in pH
when small amounts of acid or base are added to the solution. Buffers have a variety of uses – most
importantly in the blood of humans. Because a pH that is too high or too low can denature proteins
which make up nearly all parts of your body, it’s important that your body maintain a certain pH
range. The blood does this with a carbonic acid buffer.
H+(aq) + HCO3-1(aq)  H2CO3(aq)  H2O(l) + CO2(g)
In this lab you will be testing the buffer capacity using a computer simulation.
Buffer capacity means how much acid or base a solution can absorb before it changes pH
significantly. In this case we’ll define buffer capacity as the amount of acid or base it takes to
change the pH by 2.
Procedures:
Find the following website and read the instructions:
http://michele.usc.edu/java/acidbase/acidbaseinst.html
Once you understand what all the buttons do, click on This simulator at the top of the page.
Although, the simulator graphs for you, I want you to take your own data and make your own graphs
of pH vs volume of NaOH and HCl added.
Data:

Make appropriate data tables that will allow you to
o graph pH vs volume of acid added for each buffer and water
o graph pH vs volume of base added for each buffer and water
o calculate the buffer capacity for each buffer solution
o Also remember to record the conditions you are testing for each trial.
1. Acetate Buffer
a. [HA] = 0.2
b. [A] = 0.1
2. Acetate Buffer
a. [HA] = 0.2
b. [A] = 0.2
3. Acetate Buffer
a. [HA] = 0.2
b. [A] = 2.0
4. Your choice
Analysis:
You will turn in your lab book with data tables, graphs and answers to the questions
1.
2.
3.
4.
5.
Graph pH vs volume of acid added for each buffer and water
Graph pH vs volume of base added for each buffer and water
What factors affect the buffering capacity?
Explain qualitatively how a buffer works.
Give three methods for making a buffer solution.