Chemistry 112 Buffers - Drew Rasmussen Chemistry 112L...

Drew Rasmussen
Chemistry 112L
Partner: Jay
Katri Truhler
April 14, 2011
Phosphate Buffers Lab Write-Up
A. Research Questions:
a. What is the mole ratio required to prepare your assigned buffer (pH 8.00, 0.05M)?
b. What was the experimentally measured pH of your buffer?
c. What were the calculated pH’s for your Base + Water and Acid + Water?
B. Theoretical Approach:
a. Using the Hendersen-Hasselbach equation (an equation designed specifically for
calculating base pH, mole ratio, and K
a
values) a buffer will be created to match
an assigned pH and concentration value. By using this equation you can solve for
the required mole ratio of the assigned buffer. With the mole ratio, and the
concentration known you can then solve for the amount of acid and base (in
grams) required to prepare your buffer. Once the solution has been mixed up
using the calculated weights of acid and base, it is possible to test how the buffer
reacts to the addition of acid or base, and how this compares to adding an acid or
base to pure water.
C. Observations and Results:

c. The NaOH and HCl used were both 0.1M. Found in white bottles on top of work
station shelf.
d. The masses were carefully weighed out to within + or – 0.001g of the calculated
weight and put in a 100mL volumetric flask. They dissolved fairly easily with
some shaking. The buffer solution is clear. No apparent smell.