PSI AP Chemistry
Chapter Problems Part D: Acid-Base Reactions
Name_________________________
Classwork:
1. A student is in possession of an unknown organic acid that is one of the acids
below:
H2C2O4
H2C4H4O5
The student dissolves 3.00 grams of the acid in water to prepare a 50 mL
solution of the acid and then fully titrates the acid with standardized 0.4 M
KOH. The student found that 112 mL was needed to reach the endpoint of the
titration.
a) Write a balanced reaction of the base with either of the two acids
shown above:
b) What is the molar mass of the acid and identify the acid.
c) How many mL of 0.8 M KOH would be needed to titrate the acid
found in “b”?
d) How many mL of 0.4 M KOH would have been needed to titrate an
equivalent molar amount of the other acid?
e) How many mL of 0.4 M KOH would have been needed to titrate a
solution of HCN assuming an equal number of moles of HCN as
there were of the acid found in “b”?
2. Write the proper reaction for the following:
a. Solid calcium hydroxide is added to an ammonium chloride solution
b. Aqueous potassium hydroxide is used to titrate a hydroiodic acid
solution.
c. A nitrous acid solution is added to a sodium carbonate solution
3. Citric acid (H3C6H5O7) is an important metabolite in living organisms.
a. What is the conjugate base of citric acid?
b. Write the reaction of citric acid with water. (assume only one H is
donated)
c. How many mL of 0.4 M NaOH would be needed to convert all citric
acid into HC6H5O72-?
d. How many mL of 0.4 M NaOH would be needed to convert all citric
acid to the citrate ion (C6H5O73-)?
e. Which of the following is amphoteric (H2C6H5O7- or C6H5O73-)? Justify
your answer.
4. A 0.2 M acetic acid (HC2H3O2) solution dissociates 1.5% in water.
a. What is the equilibrium concentration of the acetate ion in such a
solution?
b. If acetic acid were a strong acid (IT’S NOT!), what would be the
concentration of acetate ion in the solution?
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AP Chemistry
Mole Concept, Reactions, Stoichiometry
Answers
Classwork:
1. A student is in possession of an unknown organic acid that is one of the acids
below:
H2C2O4
H2C4H4O5
The student dissolves 3.00 grams of the acid in water to prepare a 50 mL
solution of the acid and then fully titrates the acid with standardized 0.4 M
KOH. The student found that 112 mL was needed to reach the endpoint of the
titration.
a) Write a balanced reaction of the base with either of the two acids
shown above:
H2C2O4 + 2OH-  2H2O + C2O42H2C4H4O5 + 2OH-  2H2O + C4H4O52b) What is the molar mass of the acid and identify the acid.
134 g/mol = H2C4H4O5
c) How many mL of 0.8 M KOH would be needed to titrate the acid
found in “b”?
56 mL
d) How many mL of 0.4 M KOH would have been needed to titrate the
other acid?
112 mL
e) How many mL of 0.4 M KOH would have been needed to titrate a
solution of HCN assuming an equal number of moles of HCN as
there were of the acid found in “b”?
56 mL
2. Write the proper reaction for the following:
a. Solid calcium hydroxide is added to an ammonium chloride solution
Ca(OH)2(s) + 2NH4+(aq)  2NH3(aq) + Ca2+(aq) + 2H2O(l)
b. Aqueous potassium hydroxide is used to titrate a hydroiodic acid
solution.
OH-(aq) + H+(aq)  H2O(l)
c. A nitrous acid solution is added to a sodium carbonate solution
HNO2(aq) + CO32-(aq)  H2CO3(aq) + NO2-(aq)  CO2(g) + H2O(l) + NO2-(aq)
3. Citric acid (H3C6H5O7) is an important metabolite in living organisms.
a. What is the conjugate base of citric acid?
H2C6H5O7Also acceptable:
HC6H5O7-2
C6H5O7-3
b. Write the reaction of citric acid with water. (assume only one H is
donated)
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AP Chemistry
Mole Concept, Reactions, Stoichiometry
H3C6H5O7(aq) + H2O(l)  H2C6H5O7-(aq) + H3O+(aq)
c. How many mL of 0.4 M NaOH would be needed to convert all citric
acid in a 10 mL 0.5 M citric acid solution into HC6H5O72-?
25 mL
d. How many mL of 0.4 M NaOH would be needed to convert all citric
acid in the previous problem to the citrate ion (C6H5O73-)?
37.5 mL
e. Which of the following is amphoteric (H2C6H5O7- or C6H5O73-)? Justify
your answer.
H2C6H5O7- as it can both accept H+ ions and donate them while the
citrate ion can only act as a base
4. A 0.2 M acetic acid (HC2H3O2) solution dissociates 1.5% in water.
a. What is the equilibrium concentration of the acetate ion in such a
solution?
0.003 M
If acetic acid were a strong acid (IT'S NOT!!!), what would be the
concentration of acetate ion in the solution?
0.2 M
www.njctl.org
AP Chemistry
Mole Concept, Reactions, Stoichiometry