CHEM 417 Practice Problems Fall
2009
Set 6
Problem 9-2:
Calculate the pH of the following:
a) 1.0 × 10-3 M HBr
b) 1.0 × 10-2 M KOH
Problem 9-3:
Calculate the pH of 5.0 × 10-8 M HClO4. What fraction of the total H+ in this solution is derived
from dissociation of water?
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CHEM 417 Practice Problems Fall
2009
Problem 9-5:
Write the chemical reaction whose equilibrium constant is
a)
b)
c)
d)
Ka for benzoic acid, C6H5CO2H
Kb for benzoate ion, C6H5CO2Kb for aniline, C6H5NH2
Ka for anilinium ion, C6H5NH3+
2
CHEM 417 Practice Problems Fall
2009
Problem 9-6:
Find the pH and fraction of dissociation (α) of a 0.100 M solution of the weak acid HA with Ka =
1.00 × 10-5.
Problem 9-8:
Find the pH and concentration of (CH3)3N and (CH3)3NH+ in 0.060 M solution of
trimethylammonium chloride.
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CHEM 417 Practice Problems Fall
2009
Problem 9-19:
Find the pH and fraction of association (α) of a 0.100 M solution of the weak base B with Kb =
1.00 × 10-5.
Exercise 9-B:
Calculate the pH of
a) 1.0 × 10-8 HBr
b) 1.0 × 10-8 H2SO4 (H2SO4 dissociates completely to 2H+ and SO42- at this low
concentration)
Exercise 9-J (a, c, d):
Find the pH of a solution prepared by dissolving 1.00 g of glycine amide hydrochloride (Table 92) plus 1.00 g of glycine amide in 0.100 L.
What would the pH be if the solution (above) were mixed with 5.00 mL of 0.100 M HCl?
What would the pH be if the solution (above) were mixed with 10.00 mL of 0.100 M NaOH?
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CHEM 417 Practice Problems Fall
2009
Owens Practice Problem
Consider a 1.00 L buffer prepared by mixing 6055 mg of Tris
[tris(hydroxymethyl)aminomethane] (pKa’ = 8.3) in the free-base form (FW = 121.1 g/mol) and
38 mM HCl.
a)
b)
c)
d)
What is the pH of the buffer?
What would the pH be if we had added 48 mM of HCl?
What would the pH be if we had added 1.00 mL of 0.100 M NaOH?
Could you use a Tris buffer system to prepare a buffer at pH 7.00? Why or why not?
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CHEM 417 Practice Problems Fall
2009
Problem 9-7:
BH+ClO4- is a slat formed from the base B (Kb = 1.00 × 10-4) and perchloric acid. It dissociates
into BH+, a weak acid, and ClO4 -, which is neither an acid nor a base. Find the pH of 0.100 m
BH+ClO4-.
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