Name: __________________________________________
Date: ________________ Period: ____
REVIEW Unit 4 Test (Chp 4): Aqueous Reactions and Solution Stoichiometry
Multiple Choice (20 questions) (50% of score)
polyatomic ions (names, charges, formulas)
6 strong acids (what does it to say a “strong” “acid” ?)
strong bases (group I and Ca, Ba, Sr with hydroxide, OH–) (what is a “strong” “base” ?)
electrolytes (strong, weak, non) (and what particles are actually in solution)
ALWAYS soluble (group I , NH4+ , NO3–)
Typically soluble (Cl– , Br– , I– except with AP: Ag+ & Pb2+)
NET ionic equations (comp – diss – cross – net – bal)
oxidation numbers of elements in compounds (like what is the ox. # of C in oxalate ion C2O42– ?)
redox reactions (LEO says GER)
activity of metals (which metals are least active – or – which metals do not lose electrons as well)
gas forming reactions ( ____ reacted with ____ will form which gas – H2(g) or CO2(g) )
solution stoichiometry ( L  g ) ( g  L ) ( g and L  M ) ( dilutions M1V1 = M2V2 )
Free Response (35 points) (4 questions: 3 long, 1 short) (50% of score)
1) lab question: solution preparation, gravimetric analysis of precipitate to find % by mass (8 pts)
2) redox reactions, oxidation numbers, and oxidation/reduction half reactions (3 pts)
3) lab question: qualitative analysis of unknown solutions by precipitation (9 pts)
4) write 3 NET ionic equations from verbal descriptions, predict products, and balance (15 pts)
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Section I Multiple Choice
NO Calculator Allowed
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How many grams of methanol, CH3OH (MW = 32.0 g∙mol–1) are there in 500. mL of a 0.500 M CH3OH
solution?
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27. Beaker X and beaker Y each contain 1.0 L of solution, as shown above. A student combines the
solutions by pouring them into a larger, previously empty beaker Z and observes the formation
of a white precipitate.
Assuming that volumes are additive, which of the following sets of solutions could be
represented by the diagram above?
Beaker X
Beaker Y
Beaker Z
(A) 2.0 M AgNO3
2.0 M MgCl2
4.0 M Mg(NO3)2 and AgCl(s)
(B) 2.0 M AgNO3
2.0 M MgCl2
2.0 M Mg(NO3)2 and AgCl(s)
(C) 2.0 M AgNO3
1.0 M MgCl2
1.0 M Mg(NO3)2 and AgCl(s)
(D) 2.0 M AgNO3
1.0 M MgCl2
0.50 M Mg(NO3)2 and AgCl(s)
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Section II Free Response
Calculator Allowed
CLEARLY SHOW THE METHODS USED AND STEPS INVOLVED IN YOUR ANSWERS. It is to
your advantage to do this, because you may earn partial credit if you do and little or no credit if you do
not. Attention should be paid to significant figures.
1.
A student is assigned the task of preparing 50. mL of 6 M HNO3 to use in an experiment.
(a) The student is provided with a stock solution of 16 M HNO3 , two 100 mL graduated cylinders
that can be read to ±1 mL, a 100 mL beaker that can be read to ±10 mL, safety goggles, rubber
gloves, a glass stirring rod, a dropper, and distilled H2O.
(i) Calculate the volume, in mL, of 16 M HNO3 that the student should use for preparing 50. mL
of 6 M HNO3 . (1)
(ii) Briefly list the steps of an appropriate and safe procedure for preparing the 50. mL of
6 M HNO3. Only materials selected from those provided to the student (listed above)
may be used. (2)
(iii) Explain why it is not necessary to use a volumetric flask (calibrated to 50.00 mL ±0.05 mL)
to perform the dilution. (1)
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In a second experiment, a student is given 2.94 g of a mixture containing anhydrous MgCl2 and KNO3.
To determine the percentage by mass of MgCl2 in the mixture, the student uses excess AgNO3(aq) to
precipitate the chloride ion as AgCl(s).
(b) Starting with the 2.94 g sample of the mixture dissolved in water, briefly describe the steps
necessary to quantitatively determine the mass of the AgCl precipitate. (2)
(c) The AgCl precipitate is filtered, washed, dried, and weighed to constant mass in a filter crucible.
The student determines the mass of the AgCl precipitate to be 5.48 g.
On the basis of this information, calculate each of the following.
(i) The number of moles of MgCl2 in the original mixture (2)
(ii) The percent by mass of MgCl2 in the original mixture (1)
2. An aluminum metal container, Al(s), filled with an aqueous solution of copper(II) sulfate, CuSO4(aq)
eventually developed a leak. It is proposed that a redox reaction occurred that dissolved the
aluminum metal forming soluble aluminum sulfate, Al2(SO4)3(aq) and solid copper, Cu(s).
(a) Write a balanced equation for the overall reaction described above. Indicate whether the
Cu in CuSO4 is oxidized or whether it is reduced in the reaction. Justify your answer. (2)
(b) Write the balanced half reaction for the oxidation reaction showing electrons. (1)
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3. The identity of an unknown solid is to be determined. The compound is one of the seven salts in the
following table.
Al(NO3)3•9H2O
BaCl2•2H2O
CaCO3
NaCl
BaSO4
Ni(NO3)2•6H2O
CuSO4•5H2O
Use the results of the following observations or laboratory tests to explain how each compound in
the table may be eliminated or confirmed. The tests are done in sequence from (a) through (e).
(a) The unknown compound is white. In the table below, cross out the two compounds that can be
eliminated using this observation. Be sure to cross out these same two compounds in the tables
in parts (b), (c), and (d). (2)
Al(NO3)3•9H2O
BaCl2•2H2O
CaCO3
NaCl
BaSO4
Ni(NO3)2•6H2O
CuSO4•5H2O
(b) When the unknown compound is added to water, it dissolves readily. In the table below, cross
out the two compounds that can be eliminated using this test. Be sure to cross out these same
two compounds in the tables in parts (c) and (d). (2)
Al(NO3)3•9H2O
BaCl2•2H2O
CaCO3
NaCl
BaSO4
Ni(NO3)2•6H2O
CuSO4•5H2O
(c) When AgNO3(aq) is added to an aqueous solution of the unknown compound, a white
precipitate forms. In the table below, cross out each compound that can be eliminated using
this test. Be sure to cross out the same compound(s) in the table in part (d). (1)
Al(NO3)3•9H2O
BaCl2•2H2O
CaCO3
NaCl
BaSO4
Ni(NO3)2•6H2O
CuSO4•5H2O
(d) When the unknown compound is carefully heated, it loses mass. In the table below, cross out
each compound that can be eliminated using this test. (1)
Al(NO3)3•9H2O
BaCl2•2H2O
CaCO3
NaCl
BaSO4
Ni(NO3)2•6H2O
CuSO4•5H2O
(e) Describe a test that can be used to confirm the identity of the unknown compound identified in
part (d). Limit your confirmation test to a reaction between an aqueous solution of the unknown
compound and an aqueous solution of one of the other soluble salts listed in the tables above.
Describe the expected results of the test; include the formula(s) of any product(s).
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4. For each of the following three reactions, in part (i) write a balanced equation for the reaction and in
part (ii) answer the question about the reaction. In part (i), coefficients should be in terms of lowest
whole numbers. Assume that solutions are aqueous unless otherwise indicated. Represent
substances in solution as ions if the substances are extensively ionized. Omit formulas for any ions
or molecules that are unchanged by the reaction. You may use the empty space for scratch work, but
only equations that are written in the answer boxes provided will be graded.
(a) A solution of barium hydroxide is added to a solution of acetic acid (ethanoic acid).
(i) Balanced equation: (4)
(ii) Which substance is a weak electrolyte. Explain. (1)
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(b) A solution of potassium sulfide is added to a solution of iron(III) chloride.
(i) Balanced equation: (4)
(ii) Classify this reaction in two ways. (1)
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(c) Excess nitric acid is added to solid sodium bicarbonate.
(i) Balanced equation: (4)
(ii) If this reaction takes place in a rigid sealed container, what change (if any) is observed in the
pressure inside the container? (1)
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ANSWER KEY
1. 2011
2008
#2(a)
(dilution)
#2(d)(e)
(gravimetric analysis)
2. 2006B #8(a) (edited)
3. 2008B #5
4.
(a) NH4+ b/c it donates a proton (H+) (Bronsted-Lowry)
(b) precipitation, double replacement
(c) pressure increases due to gas produced in reaction.
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