CHEMISTRY 102
HOUR EXAM II
1.
Fall 2014
Page 1
Which of the following statements about hybrid orbitals is true?
a. Valence atomic orbitals always combine with inner core atomic orbitals to produce
hybrid orbitals.
b. The orientation in space of the hybrid orbitals is identical to the orientation in space
of the atomic orbitals from which they are formed.
c. An sp2 hybrid orbital from one atom can overlap to form a bond with an sp3 hybrid
orbital from another atom.
d. Overlap of hybrid orbitals form π bonds.
e. Atoms which are sp2 hybridized form 2 pi bonds.
2.
A widely used herbicide is atrazine, C8N5ClH14, whose skeletal structure is shown
below. Complete a Lewis structure for this organic compound.
H
H C
H
C
H
N
1
C
N
H
H C H
H
N
Cl
C
N
C H H
H N C
C
H
H H
Which of the following statements concerning the Lewis structure for atrazine is false?
a. Atrazine has zero atoms which are sp hybridized.
b. Eight of the carbon and nitrogen atoms in atrazine have at least one unhybridized p
atomic orbital.
c. There are 28 sigma (σ) bonds and 3 pi (π) bonds in the Lewis structure.
d. The nitrogen atom labeled 1 is sp3 hybridized.
e. All the carbon-hydrogen bonds in atrazine are formed from overlap of sp3 hybrid
orbitals from carbon with 1s orbitals from hydrogen.
3.
You find a bottle on the shelf in the Chem 103 lab. The label says “0.10 M MgSO4.”
Which of the following statements best describes what is in the bottle?
a. The MgSO4 is a solid on the bottom of the bottle because it is not soluble in water.
b. There are MgSO4 molecules floating around in solution.
c. There are magnesium ions, sulfur ions, and oxygen ions floating around in
solution.
d. There are magnesium ions and sulfate ions floating around in solution.
CHEMISTRY 102
HOUR EXAM II
4.
A solution of 1.0 M KBr is diluted. Which of the following happens during the dilution?
a.
b.
c.
d.
e.
5.
molarity increases; volume is constant; moles of KBr decrease
molarity increases; volume increases; moles of KBr is constant
molarity decreases; volume decreases; moles of KBr is constant
molarity decreases; volume increases; moles of KBr is constant
molarity increases; volume is constant; moles of KBr increase
When aluminum metal is heated with an element from Group 6A of the periodic table, an
ionic compound forms. When the experiment is performed with an unknown Group 6A
element, the product is 18.55% Al by mass. What is the formula of the compound?
a. AlS3
6.
b. Al2S3
c. Al2Se3
d. Al2Te3
e. Al3S2
Which of the following gas samples (a-d) has/have the largest average kinetic energy and
has/have the fastest average velocity for the gas molecules in the gas sample?
a.
b.
c.
d.
e.
7.
Fall 2014
Page 2
1.0 mol of CO2(g) at P = 1.0 atm and T = 0.C
1.0 mol of F2(g) at P = 1.0 atm and T = 0.C
1.0 mol of N2(g) at P = 1.0 atm and T = 100.C
1.0 mol of Cl2(g) at P = 1.0 atm and T = 100.C
The gas samples in answers c and d both have the same average kinetic energy and
have the same average molecular velocity.
Consider 2 different containers each filled with two moles of Ne(g). One of the
containers is rigid and is of constant volume; the other container is flexible (like a
balloon) and is capable of changing its volume in order to keep the external pressure and
internal pressure equal to each other. If you raise the temperature in both containers,
which of the following is true concerning the pressure and density of the gas inside each
container? Assume a constant external pressure.
a. Rigid container: Pressure and density both increase;
Flexible container: Pressure and density are both constant.
b. Rigid container: Pressure is constant, density decreases;
Flexible container: Pressure increases, density decreases.
c. Pressure increases and density is constant in both containers.
d. Rigid container: Pressure increases, density decreases;
Flexible container: Pressure increases, density is constant.
e. Rigid container: Pressure increases, density is constant;
Flexible container: Pressure is constant, density decreases.
CHEMISTRY 102
HOUR EXAM II
8.
Fall 2014
Page 3
Consider the following balanced reaction:
2 C3H6(g) + 2 NH3(g) + 3 O2(g)  2 C3H3N(g) + 6 H2O(g)
When 5.0 mol of C3H6, 5.0 mol of NH3 and 6.0 mol of O2 are reacted, 3.0 mol of C3H3N
are actually produced. What is the percent yield of the reaction?
a. 33%
9.
e. 75%
b. row 3
c. row 7
d. row 8
e. row 9
b. 0.271 g
c. 0.367 g
d. 0.135 g
e. 0.162 g
Consider an organic compound which contains only carbon, hydrogen, and oxygen.
Combustion of 10.68 g of the compound yields 16.01 g CO2 and 4.37 g H2O. What is the
mass percent of hydrogen in this compound?
a. 3.87% H
12.
d. 67%
Bismuth aluminate (Al6Bi2O12) is a medication used to treat upset stomachs. If 500.0 mg
of bismuth aluminate is digested, calculate the mass of bismuth consumed. Bi is element
#83 and the molar mass of Al6Bi2O12 is 771.88 g/mol.
a. 0.500 g
11.
c. 60.%
Consider a classroom containing ten evenly-spaced rows of students. If a student in
row 1 releases laughing gas (N2O) and a student in row 10 simultaneously releases a
lachrymator (a gas which causes tears) with molar mass 176, in which row do the
students first laugh and cry at the same time? Hint: the molar mass of the lachrymator is
4 times greater than the molar mass of N2O, i.e., molar mass lachrymator = 4 × molar
mass N2O.
a. row 2
10.
b. 50.%
b. 2.98% H
c. 5.67% H
d. 3.23% H
e. 4.58% H
Consider an organic compound which contains only carbon, hydrogen, and oxygen.
Combustion of 10.68 g of the compound yields 16.01 g CO2 and 4.37 g H2O. If the
molar mass of the compound is between 250 g/mol and 280 g/mol, which of the
following is the molecular formula?
a. C3H4O3
b. C2H3O4
d. C9H12O9
e. C6H9O12
c. C12H18O6
CHEMISTRY 102
HOUR EXAM II
13.
Fall 2014
Page 4
Silver sulfadiazine burn-treating cream creates a barrier against bacterial invasion and
releases antimicrobial agents directly into the wound. If 25.0 g of Ag2O (molar mass =
231.8 g/mol), is reacted with 50.0 g of C10H10N4SO2 (molar mass = 250.3 g/mol), what
mass of silver sulfadiazine, AgC10H9N4SO2 (molar mass = 357.2 g/mol), can be produced
assuming 100% yield?
Ag2O + 2 C10H10N4SO2  2 AgC10H9N4SO2 + H2O
a. 100. g
14.
16.
d. 35.7 g
e. 71.4 g
b. 46.7%
c. 62.2%
d. 75.0%
e. 87.1%
A roach killer, dibutyl succinate, was analyzed and found to be composed of 62.58% C,
9.63% H and 27.79% O. What is the empirical formula of dibutyl succinate?
a. C3H5O
b. C6H11O2
d. C8H12O6
e. C4H6O3
c. C5H9O3
45.0 mL of 5.50 M KOH are required to react completely with 22.0 mL of an H2SO3
solution. What is the molarity of the H2SO3 solution? H2SO3 is a diprotic acid.
a. 22.5 M
17.
c. 38.5 g
At elevated temperatures, sodium chlorate decomposes to produce sodium chloride and
oxygen gas. A 0.8765-g sample of impure sodium chlorate was heated until the
production of oxygen gas ceased. The oxygen gas collected over water occupied 57.2
mL at a temperature of 22°C and a total pressure of 734 torr. Calculate the mass percent
of NaClO3 in the original sample. At 22°C, the vapor pressure of water is 19.8 torr and
assume 100% yield in the reaction.
a. 18.0%
15.
b. 77. 0 g
b. 5.63 M
c. 2.72 M
Which of the following statements is false?
a. In XeF4, the central Xe atom is sp3 hybridized.
b. In SF6, the central S atom is d2sp3 hybridized.
c. In PCl5, the central P atom is dsp3 hybridized.
d. In CO2, the central C atom is sp hybridized.
e. In SO3, the central S atom is sp2 hybridized.
d. 1.34 M
e. 11.3 M
CHEMISTRY 102
HOUR EXAM II
18.
Fall 2014
Page 5
On a typical August day in Champaign, the temperature is 35oC and the relative humidity
is 90%. A 10.0 L sample of air on this 35C day contains 0.356 g of H2O(g). From this
data, calculate the partial pressure of water on a 35C day having a relative humidity of
90%.
a. 62.3 torr
b. 28.5 torr
c. 12.6 torr
d. 37.9 torr
e. 684 torr
_____________________________________
Consider the following information for the next three questions. 100.0 mL of 0.100 M lead(II)
nitrate is added to 75.0 mL of 0.100 M ammonium phosphate and a precipitate forms.
19.
Which of the following is the correct net ionic equation for the precipitation reaction?
a. 3 Pb2+(aq) + 2 PO43 (aq)  Pb3(PO4)2(s)
b. Pb2+(aq) + PO42 (aq)  PbPO4(s)
c. Pb2+(aq) + 2 PO4 (aq)  Pb(PO4)2(s)
d. NH42+(aq) + 2 NO3 (aq)  NH4(NO3)2(s)
e. NH4+(aq) + NO3 (aq)  NH4NO3(s)
20.
21.
How many moles of precipitate form assuming 100% yield?
a. 0.0100 mol
b. 0.00750 mol
d. 0.00333 mol
e. 0.00250 mol
c. 0.00500 mol
Calculate the molarity of the ammonium ions after precipitation is complete.
a. 0.100 M
b. 0.250 M
c. 0.0429 M
d. 0.300 M
e. 0.129 M
____________________________________
22.
A compound or ion has delocalized  electrons resulting in equivalent bonds to oxygen.
All of the bonds in this compound or ion are stronger than single bonds yet are
significantly weaker than double bonds. Which of the following could be this compound
or ion?
a. CO2
b. NO2+
c. SO32−
d. NO3−
e. XeO3
CHEMISTRY 102
HOUR EXAM II
23.
Fall 2014
Page 6
Under which of the following conditions will a sample of SO2(g) behave most ideally?
a. 40 K, 500 atm
24.
d. 4000 K, 500 atm
b. 0.045 mol
c. 0.13 mol
d. 0.089 mol
e. 0.10 mol
An ideal gas in a flexible container occupies a volume of 10.0 L at 38 oC and 0.20 atm. If
the gas sample is cooled to 7 oC and the volume is decreased to 3.60 L, what is the new
pressure of the gas sample?
a. 1.7 atm
26.
c. 40 K, 0.50 atm
When N2(g) reacts with F2(g), NF3(g) is produced. If 1.0 L of F2(g) is reacted with an
excess of N2(g), how many moles of NF3(g) can be produced at STP?
a. 0.030 mol
25.
b. 4000 K, 0.50 atm
b. 0.20 atm
c. 0.92 atm
d. 0.11 atm
e. 0.50 atm
Rank the following three substances from weakest to strongest electrolyte.
HNO3, C12H22O11, HC2H3O2
a. C12H22O11 < HC2H3O2 < HNO3
b. C12H22O11 < HNO3 < HC2H3O2
c. C12H22O11 < HNO3 ≈ HC2H3O2
d.
HNO3 < HC2H3O2 < C12H22O11
e. HC2H3O2 < C12H22O11 < HNO3
27.
Lithium and nitrogen react to form lithium nitride. What mass of lithium nitride can be
produced when 20.0 g of Li is reacted with excess nitrogen?
a. 33.5 g
28.
b. 41.8 g
c. 50.2 g
d. 100. g
e. 121 g
Saccharin has a molecular formula of C7H5NO3S. A 0.589 g mixture containing
saccharin and glucose was dissolved in water. The saccharin in the mixture was reacted
to convert all of the sulfur in saccharin into the sulfate ion. The sulfate ion was then
precipitated by adding an excess of barium chloride solution. The mass of BaSO4
obtained was 0.503 g. What is the mass percent of saccharin in the mixture? The molar
mass of saccharin is 183.19 g/mol, the molar mass of glucose (C6H12O6) is 180.16 g/mol,
and the molar mass of BaSO4 is 233.4 g/mol.
a. 75.0%
b. 67.0%
c. 50.0%
d. 33.0%
e. 25.0%
CHEMISTRY 102
HOUR EXAM II
29.
Fall 2014
Page 7
Which of the following statements does not describe the reaction pictured below?
a.
b.
and
combine in a 2:1 mole ratio.
is the limiting reactant.
c. The reaction produces two different products.
The reactants
d. The reactants pictured both represent diatomic elements.
30.
Consider a container holding a “real” gas at some temperature and pressure, i.e., the gas
is not behaving “ideally.” Which of the following is true regarding the measured
pressure and the measured volume of the “real” gas as compared to the pressure and the
volume of the container if the gas were behaving “ideally?” Hint: look at the van der
Waals equation given on the constants/equations page of this exam.
a. Pmeasured > Pideal; Vmeasured > Videal
b. Pmeasured > Pideal; Videal > Vmeasured
c. Pideal > Pmeasured; Vmeasured > Videal
d. Pideal > Pmeasured; Videal > Vmeasured
31.
My answers for this Chemistry 102 exam should be graded with the answer sheet
associated with:
a. Form A
b. Form B
c. Form C
d. Form D
e. Form E