Buffer Problems
1. What is the pH of a buffer solution that is 0.25 M in HF and 0.10 M
in NaF? (Ka for HF is 6.8 x 10-4)
2. What is the final pH if 50.0 mL of 0.050 M NaOH is added to 50.0 mL
of the buffer solution in problem #1?
3. Determine the pH of a buffer that is 0.25 M in NH3 and 0.50 M in
NH4Cl. (Kb for NH3 is 1.79 x 10-5)
4. A buffer solution of pH 8.50 is desired.
(a)
Starting with 0.0100 mol of KCN and the usual inorganic reagents
of the laboratory, How would you prepare 1.00 L of the buffer
solution? Ka for HCN is 4.93 x 10-10.
(b)
By how much would the buffer change after the addition of 5 x
10-5 mol HClO4 to 100.0 mL of the buffer?
(c)
By how much would the buffer change after the addition of 5 x
10-5 mol NaOH to 100.0 mL of the buffer?
(d)
By how much would the buffer change after the addition of 5 x
10-5 mol to 100.o mL of pure water?
Answers:
1.
2.
3.
4.
2.77
2.80
8.95
A) dissolve 0.651 grams of KCN and 0.318 grams of HCl in enough
water to make 1.0 L of solution.
B) 0.26
C) 0.16
D) 3.70