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I-12
B.
Commercial pH 7.00 Buffer Solutions
1.
a.
Using the volumes of HCl and NaOH required to change the pH of the 25 mL buffer samples
1
full pH unit, determine the buffer capacity of each HA and A
-
(in mol L
-1
) of:
i.
the acetate buffer solution. (0.5 marks)
ii.
the commercial pH 7.00 buffer solution. (0.5 marks)
b.
Use the above information to explain why it is important that the pH electrode be washed well
with deionized water before it is placed into the standard buffer solutions. (Assume that each
bottle of standard buffer solution contains 50 mL.) (0.5 marks)
2.
A 1.00 M solution of an unknown monoprotic acid is titrated with NaOH. When 85.0 % of this weak
acid has reacted, the pH of the resulting solution at equilibrium is 5.33. Determine the K
a
for this
weak acid. (1.0 mark)
ASSESSMENT
Performance
(1.0 mark):
Laboratory Report
(9.0 marks):
Deductions
(if any):
TOTAL
(10.0 marks):
