This titration curve applies to acetic acid,
has a pKa of 4.6.
A. Prior to addition of any [OH] what is the pH of a solution of 150 mM
?
Solution: The reaction is
Where C = 0.15.
therefore
For such a high initial concentration we can assume that C >> x,
pH = _____________________________.
B. At what [OH] concentration will the buffering capacity of the solution be
maximal?
What is the pH at the point where the buffer strength is maximum?
Please indicate that point on the titration curve using an arrow and the label
BUFFER.
Solution: The maximum buffer strength will be reached when the concentrations of
the acid and conjugate base are equal. This will occur when 50% of the initial
has been converted. Thus, we must add 75 mM concentration of OH. At this buffer
condition the pH = pKa = 4.6
[OH] = ____0.075_ for max buffer.
pH = __4.6________________________.
C. What concentration of [OH-] must be added to reach the equivalence point?
What is the pH at the equivalence point for this acid-base equilibrium?
Please indicate the equivalence point on the diagram using an arrow and the
label EQ POINT.
Solution: The equivalence point will reached when all of the
has

been converted to the conjugate base. This will occur when [OH ] = 150 mM.
where
For such a high concentration we can assume that
Eq point at [OH] = ______0.150_____________.
pH = _______8.89_______.