Problem 1
What is the pH of a 291mL sample of 2.993M benzoic acid (C6H5COOH)
(Ka=6.4x10-5)?
Problem 2
A 489mL sample of 0.5542M HNO3 is mixed with 427mL sample of NaOH (which
has a pH of 14.06). What is the pH of the resulting solution?
Problem 3
The Ka values at 25oC for a series of acids is given:
1.8 x 10-5
7.6 x 10-4
1.3 x 10-3
1.4 x 10-3
2.2 x 10-2
Which of the following acids has a Ka = 1.4 x 10-3?
Problem 4
Consider a solution containing 0.45M HCN and 0.69M NaCN for the next two
questions. The Ka for HCN = 6.2 x 10-10.
What is the pH of this solution?
Problem 5
Consider a solution containing 0.45M HCN and 0.69M NaCN for the next two
questions. The Ka for HCN = 6.2 x 10-10.
Now calculate the pH of this solution after 0.25 mol of NaOH is added to 1.00L of
the solution. Assume that the volume does not change.
Problem 6
Consider a 7.3 x 10-10M solution of HCl at 285 K. What is the pH of the solution?
Problem 7
For the following reaction, K < 1 at room temperature.
HOCl (aq) + HCO3- (aq) ↔ H2CO3 (aq) + OCl- (aq)
Which of the following statements is true?
A) H2CO3 is a stronger acid than HOCl.
B) HOCl is a stronger acid than H2CO3.
C) OCl- is a stronger acid than HOCl.
D) HCO3- is stronger base than OCl-.
E) More information is needed.
Problem 8
What is the pH of a solution that results from adding 0.081 mol Ca(OH)2 (s) to
1.37L of a buffer comprised of 0.21M HF and 0.21M NaF?
Problem 9
A 0.251L solution of 1.89M sulfurous acid (Ka1 = 1.5x10-2 and Ka2 = 1.0x10-7) is
titrated with 1.25M NaOH.
What will the pH of the solution be when 0.6793L of the NaOH has been added?
Problem 9
A 0.251L solution of 1.89M sulfurous acid (Ka1 = 1.5x10-2 and Ka2 = 1.0x10-7) is
titrated with 1.25M NaOH.
What will the pH of the solution be when 0.6793L of the NaOH has been added?
Problem 10
The titration of 1.00L of a 1.00M solution of the triprotic acid, H3A, with 1.00M
NaOH is shown below. It is not drawn to scale.
What is the pH at D?
H3A + H2O ↔ H3O+ + H2AH2A- + H2O ↔ H3O+ + HA2HA2- + H2O ↔ H3O+ + A3-
Ka1=3.29x10-3
Ka2=6.43x10-7
Ka3=4.25x10-10
Problem 11
The titration of 1.00L of a 1.00M solution of the triprotic acid, H3A, with 1.00M
NaOH is shown below. It is not drawn to scale.
What is the pH at C?
H3A + H2O ↔ H3O+ + H2AH2A- + H2O ↔ H3O+ + HA2HA2- + H2O ↔ H3O+ + A3-
Ka1=3.29x10-3
Ka2=6.43x10-7
Ka3=4.25x10-10
Problem 12
Consider a 0.35M solution of each of the following salts in distilled water. Will
the solution be acidic, neutral, or basic?
You may need to reference a table of Ka and Kb Tables values. .
NH4OBr:
BaClO4:
RbCH3COO:
(CH3CH2)3NHNO2:
Problem 13
How many of the following are true?
1. The buffer with the greatest buffering capacity for a phenol/sodium
phenolate buffer system will have a pH of 9.60.
2. A buffer resists pH change when base is added by converting hydroxide ions
to hydronium ions..
3. A buffered system can be formed by combining a weak acid/conjugate base
pair in solution.
4. A buffer is formed when you add HCl to NH3.
5. A buffer is formed when you add HCl to CH3COOH.
Problem 14
Which of the following solutions will produce a buffer with pH near 10.50?
1.
1.00L of 0.50M HSO4- (Ka = 1.0x10-7) + 1.00L of 0.25M KOH.
2.
2.00L 0.50M H2NNH2 (Kb = 3.0x10-6) + 2.00L 0.25M HI.
3.
0.100L 1.00M H3BO3 (Ka = 5.8x10-10) + 0.020L 2.50M HBr.
4.
0.100L of 0.50M HONH2 (Kb = 1.1x10-8) + 0.50L of 0.050M HNO3.
5.
0.500L 1.00M CH3NH2 (Kb = 4.4x10-4) + 1.00L 0.25M HI.
Problem 15
The next three problems deal with the titration of 145mL of 1.35M methylamine
CH3NH2 (Kb = 4.4 x 10-4) with 0.25M HCl.
Water will be a major species throughout the titration. The chemical
species, in addition to water, that can be found in this reaction mixture
during the titration are:
I. H+ II. OH- III. Cl- IV. CH3NH2 V. CH3NH3+
What is the pH at equivalence point?
Problem 15
The next three problems deal with the titration of 145mL of 1.35M methylamine
CH3NH2 (Kb = 4.4 x 10-4) with 0.25M HCl.
Water will be a major species throughout the titration. The chemical
species, in addition to water, that can be found in this reaction mixture
during the titration are:
I. H+ II. OH- III. Cl- IV. CH3NH2 V. CH3NH3+
What is the pH at equivalence point?
Problem 16
The next three problems deal with the titration of 145mL of 1.35M methylamine
CH3NH2 (Kb = 4.4 x 10-4) with 0.25M HCl.
Water will be a major species throughout the titration. The chemical
species, in addition to water, that can be found in this reaction mixture
during the titration are:
I. H+ II. OH- III. Cl- IV. CH3NH2 V. CH3NH3+
How many mL of HCl will need to be added to reach pH=10.64?
Problem 17
The next three problems deal with the titration of 145mL of 1.35M methylamine
CH3NH2 (Kb = 4.4 x 10-4) with 0.25M HCl.
Water will be a major species throughout the titration. The chemical
species, in addition to water, that can be found in this reaction mixture
during the titration are:
I. H+ II. OH- III. Cl- IV. CH3NH2 V. CH3NH3+
What are the major species when 783mL of HCl has been added?
Problem 18
A 0.613M solution of a weak acid has a pH of 2.670 at 309K. What is the Ka of
the weak acid?
Problem 19
Consider the following titration curve:
Which is based on the following reactions:
H3A ↔ H+ + H2AH2A- ↔ H+ + HA2HA2- ↔ H+ + A3-
How many of the following are
true?
1. The pH at point B is pKa1.
2.
The pH at point E will be the
average of pKa1 and pKa2.
3.
To the right of point F
[A3-] > [HA2-].
4.
HA2- will be a major species
at point E.
5.
The second dissociation of H+
will play a large role in the
pH level at point E.