Experiment 8 pre-lab
Ken McFarland “Buffers”, CHEM 1130, TA - Nastaran Marzijarani, Section 108, Room
1871, Will Brubacher, Thursday 2:00 pm
1. Consider a buffer made by mixing equal amounts of acetic acid and sodium acetate. Refer to
equation 8-1 and
a.
Describe the relative amounts of each of the three compounds present in
the buffer solution: As the Ksp is much less than one, the acid does not
dissociate much. Most of the acid is HOAc, with relatively little H+ or
OAc-.
b.
Predict what will happen to the concentrations of each of the three
components if a small amount of HCl is added: The [HOAc] will increase,
and the [H+] and [OAc-] will decrease.
c.
Predict what will happen if a small amount of NaOH is added: the [HOAc]
will decrease, and the [H+] and [OAc-] will increase.
2. Generate an outline of a procedure for preparing 100 mL of an acetic acid/acetate buffer.
a. Add equal amounts of HOAc and NaOAc solutions, and DI water if necessary, to
produce a 100 Ml solution.
3. If a buffer is prepared using equal amounts of HOAc and NaOAc predict what the pH of
that solution will be.
a. The pH of the buffer solution will be the pKa, or 4.7
4. If the buffer is made up to be 1.0 M in acetic acid and 1.0 M in sodium acetate, predict
how much acid will be required to change the Ph of 100 mL of the buffer by 0.1 pH units
a. 8.7 mL of 1 M acid