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CHEM 103-003
Spring 2019
Exam 3-Version A
Date: 03.27.19
100 POINTS TOTAL
NAME:_________________________________________
If you think that there is information that you need to solve a problem, PLEASE ASK. There is a
periodic table attached to the back of the exam.
Test Version = A
Instructions:
 FILL OUT and BUBBLE IN the following information on the scantron form:
o Test Version (see above)
o PDID (your UNC email ID)
o Your Last Name
Multiple Choice:
1. Which Lewis structure, although acceptable, best describes the carbonate ion?
2. The dissolving of ammonium nitrate (NH4NO3 = 80.06 g/mol) in water can be
described by the following:
NH4NO3 (s)  NH4NO3 (aq)
ΔH = +25.4 kJ
How much heat will be absorbed when 175 g of ammonium nitrate dissolve in water?
a. 55.5 kJ
b. 4450 kJ
c. 6.89 kJ
d. 11.6 kJ
3. Ozone has the formula O3. Which statement is correct concerning ozone?
a. One oxygen atom has a 1+ charge while another has a 1- charge. The third one is
neutral.
b. All three atoms are neutral.
c. Two atoms are 1- charged and the third oxygen atom is 1+ charged.
d. Two atoms are 1+ charged and the third oxygen atom is 1- charged.
4. How many atoms are present in a 0.300-mole sample of gold?
a. 4.98 x 1025
b. 1.27 x 1015
c. 1.81 x 1023
d. 6.02 x 1023
5. What is the formula mass, to the nearest whole number, for lithium nitrite, LiNO2?
a. 7 amu
b. 44 amu
c. 37 amu
d. 53 amu
6. Which is an incorrect way to interpret the balanced reaction below:
2KBrO3 → 2 KBr + 3O2
a. The reactants and products contain 2 atoms of K, 2 atoms of Br, and 6 atoms of O.
b. The reactants and products both contain 334 g.
c. 2 molecules of 2 KBrO3 produce 2 molecules of 2 KBr and 3 molecules of O2.
d. 2 moles of 2 KBrO3 produce 2 moles of 2 KBr and 3 moles of O2.
e. All of the above are correct.
7. How Changes in energy can take place in what two forms?
a. potential and kinetic energy
b. heat and work
c. thermofission and nucleosis
d. heat and temperature
8. How many molecules of carbon dioxide, CO2, comprise 2.55 grams?
a. 3.49 x 1022
b. 6.76 x 1025
c. 1.04 x 1025
d. 2.86 x 1023
9. How A chemist carries out this reaction in the laboratory, using 4.31 grams of zinc and an
excess of sulfur:
Zn + S  ZnS
From the balanced equation, she calculates that she should obtain 6.41 grams of zinc sulfide.
However, she isolates only 5.01 g of product. What is her percent yield for this reaction?
a. 67.2%
b. 86.0%
c. 78.2%
d. 128%
10. What is the formal charge on the carbon in the Lewis structure for CH3O-?
a. -1
b. -2
c. 0
d. +1
11. The label on a two-pack of Reese’s Peanut Butter® cups lists 260 Calories (kcal) of
stored chemical energy. What is this energy in kilojoules?
a. 0.062
b. 62
c. 1100
d. 0.016
12. If you had an aqueous mixture that contained Ag+, K+, and Pb2+ cations, how many
different solids could precipitate if a chloride solution was added?
a. 1
b. 2
c. 3
d. 4
e. no solids will precipitate
13. Consider the reaction below:
Fe + Br2  FeBr2
If 44.2 grams of iron react with an excess of bromine gas, what mass of FeBr2 can form?
a. 171 g
b. 3.67 x 10-3 g
c. 11.4 g
d. 272 g
14. Which compound has 24 valence electrons?
a. C3H6O
b. C2H6O
c. CO2
d. HCN
15. Determine the percent composition of Mg and O in the following compound, MgO.
a. 50.0%, 50%
b. 39.7%, 60.3%
c. 65.8%, 34.2%
d. 60.3%, 39.7%
16. Consider the reaction below. How much heat is absorbed if 5.00 moles of nitrogen react
with excess oxygen?
2 N2 (g) + O2 (g)  2 N2O (g)
ΔHrxn = +163.2 kJ
a. 32.6 kJ
b. 0.0613 kJ
c. 816 kJ
d. 408 kJ
17. Given the following chemical reaction, how many grams of CO2 will be formed if 64.0
grams of O2 react with 45.0 grams of C2H6?
2C2H6 (g) + 7O2 (g) → 4 CO2 (g) + 6H2O (g)
a. 132 grams CO2
b. 66 grams CO2
c. 50 grams CO2
d. 44 grams CO2
18. When a gas condenses, it releases heat to its surroundings. This is a(n)
process.
a. endothermic
b. exothermic
c. thermoneutral
d. exergetic
19. How many moles of CO2 are present in 56.0 grams of CO2?
a. 0.786
b. 2.00
c. 0.560
d. 1.27
20. What is the specific heat of tin if a 55.0-g sample absorbs 982 J of heat to raise its
temperature by 85.0°C?
a. 0.210 J/g°C
b. 4.59 x 106 J/g°C
c. 4.76 J/g°C
d. 85.0 J/g°C
21. The mixture of gas and air inside a cylinder reacts, releasing 300 kJ of heat. If the
system does 150 kJ of work on the piston, what is the change in total energy?
a. 450 kJ
b. –450 kJ
c. 150 kJ
d. –150 kJ
22. An industrial reactor has a heat capacity of 25.6 kJ/°C. How much will the
temperature of the reactor rise if it absorbs 455 kJ of heat energy?
a. 0.0563 °C
b. 25.6 °C
c. 17.8 °C
d. 1.16 x 104 °C
23. Determine the molar mass of the following compound, C8H9NO2.
a. 151.2
b. 137.2
c. 166.2
g/mol
g/mol
g/mol
24. Which of the following are exothermic processes?
a. melting
b. boiling
c. evaporating
d. all of the above
e. none of the above
d. 135.2
g/mol
25. A chemist carries out this reaction in the laboratory, using 4.31 grams of zinc and an
excess of sulfur:
Zn + S  ZnS
From the balanced equation, she calculates that she should obtain 6.41 grams of zinc
sulfide. However, she isolates only 5.01 g of product. What is her percent yield for this
reaction?
a. 67.2%
b. 86.0%
c. 78.2%
d. 128%
26. A skunk’s spray contains the foul-smelling compound butanethiol, C4H8S. What is the
percent by mass of sulfur in this compound (to the nearest whole percent)?
a. 8%
b. 36%
c. 55%
d. 75%
27. In order to determine the limiting reactant in a particular reaction, one must know each
of the following EXCEPT:
a. the mass of each reactant present.
b. the molar mass of each reactant present.
c. the coefficient of each reactant in a balanced equation.
d. the mass of each product formed.
e. All of the above must be known.
28. Based on the balanced equation below, how many moles of SF6 can form from the
combination of 5 moles of S and 18 moles of F2?
S + 3 F2  SF6
a. 6
b. 5
c. 18
d. 23
29. How many molecules of carbon monoxide are in 2.34 moles of carbon monoxide?
a. 1.41 x 1024
b. 2.57 x 1023
c. 1.69 x 1025
d. 2.15 x 1022
30. How much heat is required to raise the temperature of 85.0 grams of water by 15.0 °C?
a. 1280 J
b. 5.67 J
c. 15.0 J
d. 5330 J
31. Which of the following represents the freezing of water?
a. H2O(s) H2O(l) + energy
b. energy + H2O(s) H2O(l)
c. H2O(l) H2O(s) + energy
d. energy + H2O(l) H2O(s)
32. Which of these molecules does not have a lone pair on the central atom?
a. NH3
b. SF2
c. PCl3
d. CO2
33. A sample of sodium hydroxide dissolves in water, releasing heat to the surrounding
water, and causing the temperature to rise by 20 °C. If the heat change for the reaction
is –300 J, what is the heat change for the surrounding water?
a. 6,000 J·°C
b. – 20 °C
c. –300 J
d. +300 J
34. Given the following balanced chemical equation, how many grams of carbon are
needed to completely react with 75.2 g of SiO2?
SiO2 (g) + 3C (s) → SiC (s) + 2CO (g)
a. 3.76 g C
b. 15.1 g C
c. 36.0 g C
d. 45.1 g C
Useful information:
*These conversions are exact
Length
1 km = 0.6214 miles
1 m = 39.37 inches
1 m = 1.094 yards
1 ft. = 30.48 centimeters
1 in = 2.54 centimeters
Mass
1 kg = 2.205 pounds
1 lb. = 453.59 grams
1 oz. = 28.35 grams
Volume
1 L = 1000 mL
1 L = 1000 cubic centimeters (cm3)
1 L = 1.057 quarts
1 US gal = 3.785 Liters
Energy
1 J = 1 kg*m2/s2
1 calorie = 4.184 J
1 kcal = 1 Calorie
1 British thermal unit = 1055 J
1 kilowatt hour (kWh) = 3.6×106 J







5
℃ = (℉ − 32)
9
9
℉ = (℃) + 32
5
𝐾 = ℃ + 273.15
Speed of light (c) = 3.00x108m/s
Planck’s constant (h) =6.626×10-32J*s
𝑞 = 𝑚𝑠∆𝑇
𝑞 = 𝐶∆𝑇
𝑞𝑠𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒 = −𝑞𝑤𝑎𝑡𝑒𝑟
SH2O=4.184 J/g⁰C
Any compound containing an alkali metal of the ammonium ion is soluble.
Nitrates and acetates are always soluble.
Halides are soluble except when paired with Ag+, Hg22+, or Pb2+.
Sulfates are soluble except when paired with Ca2+, Sr2+, Ba2+, or Pb2+.
Hydroxides are insoluble except when paired with an alkali metal or the
ammonium ions.
Sulfides are insoluble except when paired with an alkali metal, the ammonium ion,
Ca2+, Sr2+, or Ba2+.
Carbonates and phosphates are insoluble except when paired with an alkali metal or
the ammonium ion.

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