1. Consider the effect of adding 1.0 mL of 1.0 M NaOH to 1.0 L of water. What is

Question

1. Consider the effect of adding 1.0 mL of 1.0 M NaOH to 1.0 L of water. What is the pH of this

solution before and after addition of base?

2. Consider the effect of adding 1.0 mL of 1.0 M NaOH to 1.0 L of a buffer that contains 0.1 M

HC2H3O2 and 0.1 M NaC2H3O2. What is the pH before and after the addition of base?

3. Which of the following acids would be there best choice to combine with its sodium salt to

make a solution buffered at pH 3.45? For the best choice, calculate the ratio of the conjugate

base to the acid required to attain the desired pH.

Chlorous acid pKa = 1.95

Nitrous acid pKa=3.34

Formic acid pKa= 3.74

Hypochlorous acid pKa = 7.54

4. Which of the acids in question #3 would be the best choice to create a buffer with pH = 7.35?

If you had 250.0 mL of a 0.20 M solution of the acid, what mass of the corresponding sodium

salt of the conjugate base would be required to make the buffer? (assume addition of the solid

salt would not affect the volume of the solution)

5. A 1.0 L buffer solution is 0.10 M in HF and 0.050 M in NaF. Which of the following actions

would destroy the buffer?

a) Adding 0.050 mol of HCl

b) Adding 0.050 mol of NaF

c) Adding 0.05 mol of NaOH

d) None of the above

e) More than one of the above

Explain your answer.

Explanation / Answer

pH = pKa + log [ClO-]/ [HClO]

7.35 - 7.54 = - 0.19 = log [ClO-]/ [HClO]


10^-0.19 =0.65 = [ClO-]/ 0.10

[ClO-] = 0.065 M

moles NaClO = 0.065 M x 0.500 L=0.0325
mass NaClO = 0.0325 x 74.44 g/mol=2.4 g

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