AP Chemistry
Name____________________________________
Solution Stoichiometry PRACTICE TEST 2
Date____________________
SECTION I: Multiple Choice (Time: 27 min for MC + 10 min for 2 additional questions). Select the best answer for each
question. You need not show any work. Calculators are typically not permitted on this section of the test. Today’s
test will permit the use of calculators.
1.
An unknown substance dissolves readily in water but not in benzene (a nonpolar solvent). Molecules of what
type are present in the substance?
a)
b)
c)
d)
e)
Ans: b
2.
Chapter/Section: 4.1
Difficulty: Easy
Algorithm: Yes
Chapter/Section: 4.3
Difficulty: Moderate
For the reaction 4FeCl2(aq) + 3O2(g)  2Fe2O3(s) + 4Cl2(g), what volume of a 0.890 M solution of FeCl2 is required to react
completely with 8.71 × 1021 molecules of O2?
a)
4.49 × 103 mL
b)
17.2 mL
c)
12.2 mL
d)
21.7 mL
e)
9.65 mL
Ans: d
4.
Algorithm: No
An analytical procedure requires a solution of chloride ions. How many grams of CaCl2 must be dissolved to make 2.15 L of
0.0520 M Cl–?
a)
11.54 g
b)
0.373 g
c)
6.20 g
d)
2.89 g
e)
24.8 g
Ans: c
3.
neither polar nor nonpolar
polar
either polar or nonpolar
nonpolar
none of these
Algorithm: Yes
Chapter/Section: 4.3
Difficulty: Difficult
Sulfuric acid, H2SO4, is a diprotic acid. What is the total number of moles of H + available for reaction in 3.50 L of 0.400 M
H2SO4? ? (NOTE: change answer choices to match values you changed)
a)
0.133 mole
b)
1.20 mole
c)
0.467 mole
d)
3.00 moles
e)
4.20 moles
Ans: e
Algorithm: Yes
Chapter/Section: 4.3
Difficulty: Easy
5.
The following reactions:
Pb2+ + 2I–  PbI2
2Ce4+ + 2I–  I2 + 2Ce3+
HOAc + NH3 NH4+ + OAc–
are examples of
a)
acid-base reactions
b)
unbalanced reactions
c)
precipitation, acid-base, and redox reactions, respectively
d)
redox, acid-base, and precipitation reactions, respectively
e)
precipitation, redox, and acid-base reactions, respectively
Ans: e
Algorithm: No
Chapter/Section: 4.4
Difficulty: Easy
6.
Consider the reaction between 15.0 mL of a 1.00 M aqueous solution of AgNO3 and 10.0 mL of a 1.00 M aqueous solution of
K2CrO4. When these react, a precipitate is observed. What is present in solution after the reaction is complete? Note: the solid is not
considered to be in solution.
a)
Ag+, NO3–, K+, CrO42–, water
b)
Ag+, NO3–, K+, water
c)
K+, CrO42–, water
d)
NO3–, K+, CrO42–, water
e)
water
Ans: d
Algorithm: No
Chapter/Section: 4.7
Difficulty: Moderate
7.
If all of the chloride in a 4.776-g sample of an unknown metal chloride is precipitated as AgCl with 70.90 mL of 0.2010 M
AgNO3, what is the percentage of chloride in the sample?
a)
50.52%
b)
10.58%
c)
1.425%
d)
9.454%
e)
none of the above
Ans: b
Algorithm: Yes
Chapter/Section: 4.7
Difficulty: Moderate
8.
You have 135.8 mL of a 2.50 M solution of Na2CrO4(aq). You also have 125 mL of a 2.50 M solution of AgNO3(aq). Calculate
the concentration of Na+ after the two solutions are mixed together.
a)
0.00 M
b)
1.30 M
c)
2.60 M
d)
5.00 M
e)
0.679 M
Ans: c
Algorithm: Yes
Chapter/Section: 4.7
Difficulty: Easy
9.
A 0.307-g sample of an unknown triprotic acid is titrated to the third equivalence point using 35.2 mL of 0.106 M NaOH.
Calculate the molar mass of the acid.
a)
247 g/mol
b)
171 g/mol
c)
165 g/mol
d)
151 g/mol
e)
82.7 g/mol
Ans: a
Algorithm: No
Chapter/Section: 4.8
Difficulty: Difficult
10. What mass of NaOH is required to react exactly with 25.0 mL of 3.0 M H2SO4?
a)
3.0 g
b)
0.7 g
c)
6.0 g
d)
150 g
e)
none of these
Ans: c
Algorithm: Yes
Chapter/Section: 4.8
Difficulty: Easy
11. A student weighs out 0.681 g of KHP (molar mass = 204.22 g/mol) and titrates to the equivalence point with 36.78 mL of a
stock NaOH solution. What is the concentration of the stock NaOH solution? KHP is an acid with one acidic proton.
a)
0.00333 M
b)
0.123 M
c)
0.0185 M
d)
0.0907 M
e)
none of these
Ans: d
12.
13.
14.
Chapter/Section: 4.8
Difficulty: Moderate
In which of the following does nitrogen have an oxidation state of +4?
a)
HNO3
b)
NO2
c)
N 2O
d)
NH4Cl
e)
NaNO2
Ans: b
Algorithm: No
Chapter/Section: 4.9
Difficulty: Easy
In the reaction 2Ca(s) + O2(g)  2CaO(s), which species is oxidized?
a)
O2
b)
O2–
c)
Ca
d)
Ca2+
e)
none of these
Ans: c
Algorithm: No
Chapter/Section: 4.9
Difficulty: Easy
In the reaction P4(s) + 10Cl2(g)  4PCl5(s), the reducing agent is
a)
chlorine
b)
PCl5
c)
phosphorus
d)
Cl–
e)
none of these
Ans: c
15.
Algorithm: Yes
Algorithm: No
Chapter/Section: 4.9
Difficulty: Easy
Which of the following are oxidation-reduction reactions?
16.
17.
18.
I.
PCl3 + Cl2  PCl5
II.
Cu + 2AgNO3  Cu(NO3)2 + 2Ag
III.
CO2 + 2LiOH  Li2CO3 + H2O
IV.
FeCl2 + 2NaOH  Fe(OH)2 + 2NaCl
a)
III
b)
IV
c)
I and II
d)
I, II, and III
e)
I, II, III, and IV
Ans: c
Algorithm: No
Chapter/Section: 4.9
Difficulty:
Balance the following oxidation-reduction reaction using the oxidation number method: Fe3+ + I–  Fe2+ + I2
In the balanced equation, the coefficient of Fe2+ is
a)
1
b)
2
c)
3
d)
4
e)
none of these
Ans: b
Algorithm: No
Chapter/Section: 4.10
Difficulty: Easy
The MnO4– is often used to analyze for the Fe2+ content of an aqueous solution via the reaction
MnO4–(aq) + Fe2+(aq) + H+(aq) Fe3+(aq) + Mn2+(aq) + H2O(l)
What is the ratio of Fe2+ : MnO4– in the balanced equation?
a)
1:1
b)
2:1
c)
3:1
d)
4:1
e)
5:1
Ans: e
Chapter/Section: 4.10
Difficulty: Moderate
Given the reaction: 2MnO4– + 5H2O2 + 6H+  2Mn2+ + 8H2O + 5O2
determine the number of electrons involved in this reaction.
a)
10
b)
8
c)
6
d)
4
e)
2
Ans: a
Algorithm: No
Chapter/Section: 4.10
Difficulty: Easy
(NON-AP Format Questions)
19. Balance the following redox reaction in basic solution using the half reaction method.
O2 +
Cr3+
→
H2O2
+
Cr2O72-
20. Balance the following redox reaction in acid solution using the half reaction method.
H2O2
+
Cr2O72-
→
O2
+
Cr3+
SECTION II: Free Response
“Directions: Questions 1–3 are long free-response questions that require about 20 minutes each to answer and are
worth 10 points each. Questions 4–7 are short free-response questions that require about 7 minutes each to answer and
are worth 4 points each. Write your response in the space provided following each question. Examples and equations
may be included in your responses where appropriate. For calculations, clearly show the method used and the steps
involved in arriving at your answers. You must show your work to receive credit for your answer. Pay attention to
significant figures.”
1. A student is given the task of determining the I− content of tablets that contain KI and an inert, water-soluble sugar as
a filler. A tablet is dissolved in 50.0 mL of distilled water, and an excess of 0.20 M Pb(NO3)2(aq) is added to the solution.
A yellow precipitate forms, which is then filtered, washed, and dried. The data from the experiment are shown in the
table above.
Mass of KI tablet
0.425 g
Mass of thoroughly dried filter paper
1.462 g
Mass of filter paper + precipitate after first drying
1.775 g
Mass of filter paper + precipitate after second drying
1.699 g
Mass of filter paper + precipitate after third drying
1.698 g
(a) For the chemical reaction that occurs when the precipitate forms,
(i) write a balanced, net-ionic equation for the reaction, and
(ii) explain why the reaction is best represented by a net-ionic equation.
(b) Explain the purpose of drying and weighing the filter paper with the precipitate three times.
(c) In the filtrate solution, is [K+] greater than, less than, or equal to [NO3 −] ? Justify your answer.
(d) Calculate the number of moles of precipitate that is produced in the experiment.
(e) Calculate the mass percent of I− in the tablet.
(f) In another trial, the student dissolves a tablet in 55.0 mL of water instead of 50.0 mL of water. Predict whether the
experimentally determined mass percent of I− will be greater than, less than, or equal to the amount calculated in part
(e). Justify your answer.
2. Answer the following questions about the solubility of Ca(OH)2. NOTE: question from 2015 exam.
(a) Write a balanced chemical equation for the dissolution of Ca(OH)2in pure water.
(b) Calculate the total number of ions present in 300. mL of a 2.3-M solution of Ca(OH)2.
(c) In the box below, complete a particle representation diagram that includes four water molecules with proper
orientation around the Ca2+ ion. Represent water molecules as shown below.
7.