BUFFERS – CHEM 220 Spring 2012
1. Which of the following would you use to prepare a buffer with a pH of 4.6
SHOW PROOF for your answer to receive FULL CREDIT
a. aminobenzene
Kb = 3.98 x 10-10
b. ammonia
Ka = 5.69 x 10-10
c. 1-naphthol
Ka = 3.84 x 10-10
2. Given that the Ka for HNO2 is 7.08 x 10-4, find the [HNO2]/[NO2-] at pH equal to 5.00.
3. You were asked by your Biochemistry professor to make a buffer with a pH equal to 3.50.
You decide that you will dissolve the conjugate base in 2.00L of 2M weak acid. How many
moles of conjugate base do you need to dissolve in the weak acid?
Acids to choose from
1. citric acid
2. hypochlorous acid
3. nitrous acid
Ka1 = 7.45 x 10-4
Ka = 3.0 x 10-8
Ka = 7.1 x 10-4
4. a. Choose an acid below and determine how much of the acid in mL that you need to add to
0.800 g of the sodium salt of its conjugate base to prepare a buffer with a pH of 3.8.
3.0 M formic acid
(HCOOH)
Ka = 1.80 x 10-4
3.0 M nitrous acid (HNO2)
Ka = 7.1 x 10-4
b. What is the concentration of this buffer?