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CHEM 1A: Exam 3--Spring 2015
Name:_____________________________
INSTRUCTIONS: On the front AND back of the scantron, fill out your name and 7-digit student ID. Fill in
this information from left to right in the provided fields, and BUBBLE IN the values on the scantron. 1
point will be deducted from your exam grade for incomplete or erroneous filling of the scantron.
All questions have 1 answer unless otherwise specified. ONLY where the question specifies “MARK ALL THAT
APPLY,” may it be necessary to mark more than one answer on the Scantron. If required, you may need to
consult the periodic table or table of electronegativities provided on the last page of this exam.
MULTIPLE CHOICE QUESTIONS:
1. MARK ALL THAT APPLY: Which reaction(s) below is NOT a redox reaction?
A. 3 Br2 + 2 GaCl3 → 2 GaBr3 + 3 Cl2
B. 6 CO2 + 6 H2O → C6H12O6 + 6 O2
C. FeCl3 + 3 AgNO3 → Fe(NO3)3 + 3 AgCl
D. C2H4 + H2 → C2H6
E. None of the above. All of these reactions are redox reactions.
2. MARK ALL THAT APPLY: Select ALL of the single replacement reactions below that would NOT generate the
products spontaneously. In other words, which reactions will not occur naturally?
A. Ba(s) + Cd2+(aq) → Ba2+(aq) + Cd(s)
B. H2(g) + Mn(OH)2(aq) → 2 H2O(l) + Mn(s)
C. Hg(s) + PtCl2(aq) → HgCl2(aq) + Pt(s)
D. 2 Au(s) + Cu+2(aq) → 2 Au+1(aq) + Cu(s)
E. None of the above. All of these single replacement reactions will occur.
3. AFTER the single replacement reaction below is PROPERLY BALANCED, what is the stoichiometric coefficient on
the aluminum (Al) reactant?
____ Al + ____ W2O7 → ____ Al2O3 + ____ W
A. 2
B. 3
C. 6
D. 7
E. 14
4. Over 60 MILLION TONS of nitric acid is produced across the world annually, most of which goes towards the
production of synthetic fertilizers and explosives. The first step in synthesizing nitric acid starts with ammonia
reacting with oxygen gas according to the equation below. When properly balanced (with the smallest WHOLE
number coefficients), what is the STOICHIOMETRIC COEFFICIENT for O2 in this reaction?
____ NH3 + ? O2 → ____ NO + ____ H2O
A.
B.
C.
D.
E.
2
2.5
3
4
5
5. The next step in the synthesis of nitric acid involves nitrogen monoxide being oxidized to nitrogen dioxide:
2 NO(g) + O2(g) → 2 NO2(g)
If this reaction is performed inside a rigid container under constant temperature conditions, how will the
pressure inside the reaction vessel change?
A. The pressure will remain the same.
B. The pressure will decrease.
C. The pressure will increase.
D. Cannot determine from information provided.
6. Once nitrogen dioxide is generated, it combines with water to generate nitric acid and more nitrogen monoxide
(see reaction below), which can be re-oxidized and produce more nitric acid.
3 NO2(g) + H2O(l) → 2 HNO3(aq) + NO(g)
Assuming both gases are at constant temperature and pressure, how many liters of nitrogen monoxide can be
generated from 4.0 liters of nitrogen dioxide according to the reaction above?
A. 1.3 L
B. 2.0 L
C. 7.0 L
D. 8.0 L
E. 12 L
7. How many grams of solid MgCl2(s) would be needed to make 500. mL of a 1.00 M aqueous solution of
magnesium chloride?
A. 29.9 g
B. 47.6 g
C. 59.8 g
D. 95.2 g
E. 190. g
8. Based on the neutralization reaction below, what volume of 4.00 M NaOH solution would be needed to fully
neutralize 400. mL of 1.00 M H3PO4 solution?
3 NaOH(aq) + H3PO4(aq) → Na3PO4(aq) + 3 H2O(l)
A. 40.0 mL
B. 200. mL
C. 300. mL
D. 600. mL
E. 1200 mL
9. Relatively new lithium/sulfur batteries have doubled the energy density of lithium ion batteries. One challenge
in the development of these batteries has been preventing the formation of lithium polysulfides which affect the
performance and structural integrity of the cathode. Of the various lithium sulfides below, which contains sulfur
in the most reduced state with the most NEGATIVE oxidation number?
A. Li2S
B. Li2S2
C. Li2S4
D. Li2S6
E. Li2S8
10. What is the oxidation number at each individual vanadium (V) in the polyatomic ion, H2V2O4-1?
A. +6
B. +5
C. +3
D. +2.5
E. +2
11. The Leclanché battery, based on the reaction below, was the forerunner of the modern zinc-carbon battery.
Zn + 2 MnO2 + 2 NH4Cl → ZnCl2 + Mn2O3 + 2 NH3 + H2O
What is the OXIDIZING agent in the reaction above?
A. Zn
B. MnO2
C. NH4Cl
D. Mn2O3
E. NH3
12. The nickel-cadmium storage battery is a type of rechargeable battery that relies on the redox reaction
below:
Cd + NiO2 + 2 H2O → Cd(OH)2 + Ni(OH)2
Which component is the REDUCING AGENT in this process?
A. Cd
B. NiO2
C. H2O
D. Ni(OH)2
E. None of the above: this reaction is NOT a redox reaction.
13. Dental amalgam, a solid solution of silver and tin in mercury, was once used extensively for filling tooth cavities.
Biting on a piece of aluminum foil with a tooth containing a silver filling often causes an unpleasant, even painful
sensation based on the redox reaction below:
2 Al + 3 Hg22+ + 4 Ag → 2 Ag2Hg3 + 2 Al3+
What is the oxidizing agent in the reaction above?
A. Al
B. Hg22+
C. Ag
D. Ag2Hg3
E. Al3+
14. When properly balanced, how many electrons would the half reaction below have?
Cr2O72- → Cr3+
A. 14 electrons
B. 12 electrons
C. 9 electrons
D. 6 electrons
E. 3 electrons
15. When properly balanced under acidic conditions, how many H+ ions should be included in the oxidation half
reaction below?
MoS2 → MoO4-1 + SO42A. 24 H+
B. 16 H+
C. 8 H+
D. 4 H+
E. None—when properly balanced, this half reaction does NOT include hydrogen.
16. Consider the balanced redox reaction below:
2 MnO4- + 6 H+ + 5 H2O2 → 2 Mn2+ + 8 H2O + 5 O2
If this reaction was properly balanced under BASIC conditions (with the smallest WHOLE number coefficients),
how many water molecules would be present in the final redox reaction?
A. 14 H2O
B. 8 H2O
C. 6 H2O
D. 2 H2O
E. None—all of the water molecules would be eliminated under basic conditions.
17. Consider the reaction for the fermentation of glucose shown below:
C6H12O6(aq) → 2 CO2(aq) + 2 CH3CH2OH(aq)
Assuming STANDARD TEMPERATURE & PRESSURE, what volume of carbon dioxide gas would be produced if
the 3.50 moles of glucose were fermented?
A. 22.7 L
B. 39.7 L
C. 79.4 L
D. 159 L
E. 318 L
18. How will the density of a gas change if the gas is cooled down and the volume is decreased?
A. The density will NOT change.
B. The density will decrease.
C. The density will increase.
D. It would depend on the specific gas under study.
E. Cannot determine from the limited information provided.
19. How will the density of a gas change if the temperature is increased and the pressure decreased?
F. The density will NOT change.
G. The density will decrease.
H. The density will increase.
I. It would depend on the specific gas under study.
J. Cannot determine from the limited information provided.
20. What is the approximate density of chlorine gas at STP?
A. 1.56 g/L
B. 3.12 g/L
C. 804 g/L
D. 1.61 x 103 g/L
E. It would depend on the volume of the container.
21. Which gas particles have the LOWEST AVERAGE kinetic energy at 200˚ C?
A. He(g)
B. NH3(g)
C. CO2(g)
D. All of these gases have EQUAL average kinetic energy
E. Cannot determine from information provided
22. MARK ALL THAT APPLY: Which statement(s) below are TRUE?
A. At a constant temperature, gaseous helium atoms are ALWAYS moving FASTER than gaseous neon atoms.
B. On average, helium atoms at 200 Kelvin have double the velocity of helium atoms at 100 Kelvin.
C. With a fixed sample of gas, simultaneously increasing the temperature & decreasing the volume will cause
the pressure to go up.
D. ALL of the statements above are TRUE.
E. None of the above are true statements.
23. Which gaseous substance would have the largest “a” term in the van der Waals equation of state?
A.
B.
C.
D.
E.
24. Which substance below would display the LARGEST DEVIATIONS from IDEAL GAS BEHAVIOR?
A. F2(g)
B. Ar(g)
C. SO3(g)
D. CH3SCH3
E. CH3SOCH3
25. Under which conditions would you expect to see the LARGEST DEVIATIONS from IDEAL GAS BEHAVIOR?
A. High Pressure, High Temperature
B. Low Pressure, Low Temperature
C. High Pressure, Low Temperature
D. Low Pressure, High Temperature
E. It depends on the identity of the gas
For the remaining multiple choice questions, reference the graph of pressure versus volume at various temperatures
plotted below for a FIXED sample of an IDEAL GAS. Each question is concerned with the behavior of an ideal gas
according to the separate laws we have learned.
26. The process of EXPANDING the gas at the constant HIGHER temperature corresponds to which transition
between two points?
A. A transition from point 2 to point 1.
B. A transition from point 2 to point 4.
C. A transition from point 4 to point 2.
D. A transition from point 4 to point 3.
E. A transition from point 3 to point 1.
27. The process of HEATING the gas at CONSTANT VOLUME corresponds to which transition between two points?
A. A transition from point 2 to point 1.
B. A transition from point 4 to point 2.
C. A transition from point 3 to point 4.
D. A transition from point 1 to point 3.
E. A transition from point 2 to point 3.
FREE RESPONSE QUESTIONS: Please read each question carefully. SHOW YOUR WORK FOR PARTIAL CREDIT.
1. The Maxwell-Boltzmann distribution for Xenon gas
at 273 K, plotted to the right, shows the different
speeds of gas particles in a sample. Relative to this
curve, draw the corresponding distribution for
Helium (He) gas at 546 K.
Briefly EXPLAIN your reasoning.
2. A lungful of air (355 mL) is exhaled into a machine that measures lung capacity. If the air was exhaled from the
lungs at 1.00 atm at 98.6 oF but the machine was at ambient conditions at 755 mmHg and 23 oC, what would be
the final volume of air measured by the machine?
3. Consider the two experimental observations below:
Reaction 1: AgClO3(aq) + Fe(NO2)3(aq) → Generates a PRECIPITATE.
Reaction 2: AgClO3(aq) + Fe(NO3)2(aq) → Does NOT generate a precipitate.
Based on this information, write the balanced molecular equation for Reaction 1. BE SURE TO WRITE THE
PHASES OF THE PRODUCTS, and specify the precipitate that forms in this reaction.
4. Write the balanced combustion reaction for the fuel C8H15O2. Be sure to report the final coefficients as the
smallest whole numbers.
5. Nitroglycerin, C3H5(NO3)3, is a shock sensitive liquid that detonates through a decomposition reaction to
generate nitrogen gas, water vapor, carbon dioxide and oxygen gas. Write the balanced chemical equation for
this decomposition process.
6. Tellurium (Te) can be oxidized by chlorate (ClO3-) to synthesize orthotelluric acid (H6TeO6) and chlorine gas.
A) Balance the REDUCTION half reaction:
B) Balance the OXIDATION half reaction:
C) Assemble the half reactions above & write the OVERALL redox reaction in ACIDIC CONDITIONS:
7. Two different gases (unknowns A & B) were studied under varying conditions (States 1, 2, & 3). The table below
reports the temperatures, volumes and pressures for these different conditions, including the final column
which compares the real (measured) pressures of the gases to the expected pressures assuming ideal gas
behavior (calculated using P=nRT/V).
Temperature Volume IDEAL Pressure
REAL Pressure
Real – Ideal Pressure
Gas
State
(K)
(L)
(atm)
(atm)
Difference (atm)
1
273
5.00
4.48
4.45
-0.03
Unknown
2
273
0.500
44.8
42.4
-2.4
A
3
273
0.0500
448
692
+244
1
273
5.00
4.48
4.37
-0.11
Unknown
2
273
0.500
44.8
34.6
-10.2
B
3
273
0.0500
448
1711
+1263
A. For both gases studied, the difference between the real pressure and the ideal pressure becomes more
substantial when moving from State 1 to State 2. Explain why the deviation from ideal behavior would increase
moving from State 1 to State 2. Include in your response a discussion of the characteristics of an ideal gas
versus a real gas.
B. As the gases are compressed from State 2 to State 3, the real pressures become LARGER than the expected
(ideal) pressures. EXPLAIN this change again by citing the characteristics of an ideal gas versus a real gas.
C. Each of the different unknown gases (A & B) could be one of the six gases below.
CO2, NH3, Ar, He, O2, N2
Propose identities for the unknown gases that are consistent with the data from the table above.
Unknown A: _________________ Unknown B: _________________
Hint: There is more than one correct answer that is consistent with the data provided.
D. Based on your from part C above, which gas would have the larger a & b terms in the van der Waals equation?
Explain your reasoning by describing the different structures of the unknown gases you chose.
EXTRA CREDIT: Only attempt this challenge problem if you’ve finished and checked the rest of your exam.
Show all of your work.
The reaction below represents a transesterification to convert vegetable oil into biodiesel through the action of
methanol (CH3OH). The biodiesel can then be burned in internal combustion engines as a fuel source. Calculate the
volume of carbon dioxide gas (in liters measured at 760 mmHg and 22 oC) that would be generated from converting 1.00
liter of vegetable oil (with a density of 0.91 g/mL) to biodiesel followed by complete combustion.
REFERENCE EQUATIONS:
1 mol of an ideal gas = 22.7 L at STP: 0 oC & 0.987 atm
R = 0.08206 L·atm/mol·K = 62.37 L·mmHg/mol·K = 8.314 J/mol·K
1.00 atm = 760 mmHg = 101.3 kPa = 14.7 psi
PV = nRT
Kelvin = oC + 273.15
oC
= 5/9·(oF - 32)
Molarity = moles of solution/Volume of solution
ACTIVITY SERIES