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(Page 1 of 10) EXAM 1
Name___________________________________________________
Lab Sec. # ____; TA: ______________; Lab day/time: ___________
Winter 2011
CHEMISTRY 2A
Section 1
EXAM I
Multiple Choice
(circle one)
Instructions:
CLOSED BOOK EXAM! No books, notes, or additional scrap
paper are permitted. All information required is contained
on the exam. Place all work in the space provided. If you
require additional space, use the back of the exam. A
scientific calculator may be used (if it is a programmable
calculator, its memory must be cleared before the exam).
(1) Read each question carefully.
(2) For Parts I and II, there is no partial credit given and
only answers marked on this cover page will be graded.
(3) The last page contains a periodic table and some useful
information. You may remove it for easy access.
(4) If you finish early, RECHECK YOUR ANSWERS!
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1-9 total points:
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/ 36
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U.C. Davis is an Honor Institution
Possible Points
1.
Points
# 1–9
each)
# 10-15
(4 points)
(6 points)
each)
# 16
each)
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14.
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10-15 total points:
# 18
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/ 100
Total Score (100)
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(Page 2 of 10) EXAM 1
Part I: Multiple Choice, Concepts (4 points each)
Select the best answer and enter your choice on the cover sheet–No partial credit
1.
All carbon dioxide is found to be 27.3% carbon by mass and all carbon monoxide is found
to be 42.9 % carbon by mass.. This is an example of the Law:
A. of Conservation of Mass
B. of Multiple Proportions
C. of Definite Proportions
D. E = mc2
E. none of the above
2.
The atomic mass of bromine is 79.90. Which of the following is INCORRECT:
A.
B.
C.
D.
E.
3.
Groups, or families, on the periodic table are:
A.
B.
C.
D.
E.
4.
Bromine occurs with a variable number of neutrons.
If there are only 2 isotopes of Br, Br-79 and Br-81 there is more Br-81.
Br-79 is about 4.94 time the mass of O-16.
No bromine atoms have a mass of 79.90.
All bromine atoms contain exactly 35 protons.
vertical columns of elements with similar properties.
horizontal rows of elements with increasing atomic numbers.
named for the first elements in the series; such as "actinides."
extremely reactive with each other.
elements which all occur naturally in the same state.
Arrange the following in order of increasing oxidation state of Cl:
KCl, KClO3, KClO2 and KClO4.
A. KCl, KClO3, KClO2, KClO4
B. KCl, KClO4, KClO3, KClO2
C. KClO2, KClO3, KClO4, KCl,
D. KCl, KClO2, KClO3, KClO4
E. KClO4, KClO3, KClO2, KCl
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(Page 3 of 10) EXAM 1
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8.
(Page 4 of 10) EXAM 1
What is the average mass of one chromium atom in amu, and would any real atom of
chromium have that mass?
A. 9.27 x 10-23, No
B. 1.67 x 10-24, Yes
C. 8.635x 10-23, No
D. 52.00, Yes
E. 52.00, No
9.
For the reaction symbolized as H2O(l) + BaO(s)
water is both:
A. a reactant and the solute
B. a reactant and the solvent
C. a product and the solute
D. a product and the solvent
E. a liquid and the intermediate
Ba(OH)2(aq)
Part II: Multiple Choice, Short Calculations (6 points each)
Circle the correct answer – No partial credit
10. The number of sulfur (S6) molecules equal to the sulfur in x g of sodium sulfate (Na2SO4) is?
Na=6.02x1023 molar mass of sodium sulfate=142.04 g.mol-1
A.
xNa.1.17x10-3
B.
x/Na.2.1x10-3
C.
xNa.7.04x10-3
D.
xNa.1.9x10-2
E.
xNa
11. How many protons are present in 5 molecules of Fe2O3?
A. 2.3 x 1026
B. 380
C. 50
D. 25
E. need the isotopes to calculate.
Name
12.
(Page 5 of 10) EXAM 1
Given the chemical rxn 3 A + 7 B  3 C
Assume that initially you have 80.0 g of compound B and after the reaction is completed 118.0 g of
C are recovered. The molar mass of B is 36.7 g mol-1 and for C it is 245.0 g mol-1. Which of the
following statements is correct.
A.The theoretical yield would be 229. g, the % yield is 51.6 assuming no A was used.
B.The theoretical yield would be 534. g, the % yield is 22.1 assuming excess A.
C.The theoretical yield would be 240. g, the % yield is 49.1 assuming excess A.
D.The theoretical yield would be 229. g, the % yield is 51.5 assuming excess A.
E. The theoretical yield and % yield cannot be calculated without knowing the compounds.
13. Equal volumes of two aqueous solutions are mixed one containing 31.5 g of nitric acid per
liter and the other is 0.40 M aqueous calcium carbonate. What would be the molarity of
calcium nitrate in the final solution, assuming volumes were additive?
Molar mass of HNO3 = 63.0 g/mol
CaCO3 + 2 HNO3
A.
B.
C.
D.
E.
0.125 M
0.40 M
0.25 M
0.11 M
0.20 M
Ca(NO3)2 +
CO2 +
H 2O
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(Page 6 of 10) EXAM 1
14. Calculate the mass of carbon dioxide produced when 20.0 gal of gasoline=octane (C8H18) is
burned in excess oxygen. 1 gal=3.785L and assume density of octane is 0.800 g/mL molar mass
of octane is 114 g mol-1
A. 1.3x104 grams CO2
B. 1.87x105 grams CO2
C. 2.34x104 grams CO2
D. 23.4 grams CO2
E. 186.6 grams CO2
15. A 165.0 mg sample of a mixture of sodium nitrate and aluminum chloride is dissolved in 100 mL of
water. When excess silver perchlorate is added to the solution all the chloride is precipitated
out of solution as 258.3 mg of silver chloride. What is the mass percent of aluminum chloride in
the mixture?
A. 48.53%
B. 72.8 %
C. 534%
D. 70.2%
E. 27.4%
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(Page 7 of 10) EXAM 1
Part III: Long Answer
Please show all work for calculations – Partial credit may be given
16. (10 points) Suppose that in nature the element R is made up of two isotopes R-88 and R-90.
A. Calculate the fraction of each isotope in R if the atomic mass of R is 89.25.
B. Calculate the ratio of R-88 atoms to R-90 atoms.
C. Calculate the mass % composition of R-90 in R.
D. Calculate the atomic mass if the % of R-90 was 60.0%
E. Calculate the exact mass of R-88 relative to O-16 given the following mass ratios
88R
17
19F
9
=4.679
19F
9
16O
6
= 1.1875
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(Page 8 of 10) EXAM 1
17. (9 points) Consider the following reaction?
PCl5 + 4H2O  H3PO4 + 5HCl
x is the moles of hydrochloric acid produced in the reaction when 50.0 g of phosphoric acid is
produced.
A. What is the value of x?
B. When x moles of HCl is produced how many g of H2O must have been used?
C. If the final solution has a volume of 365.0 mL and a density of 1.08 g/mL what is the
molarity H3PO4 in the final solution?
D. What is the molarity of HCl in the final solution?
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(Page 9 of 10) EXAM 1
18. (9 points) want to make 500 mL of 15.0% by mole HCl(aq) with a density of 1.15 g/mL.
a)
Assuming we have a 100 moles of solution how many grams of solution do we have?
b)
How many liters of solution would there be in the 100 moles?
c)
What is the molarity of the HCl solution?
d)
What volume of 32.0 M HCl would I need to make the 500 mL of 15.0% by mole
HCl(aq)?
…………………………………………………………………………………………………………………………………………………………
A) Grams of solution in 100 moles of solution:
B) Liters of solution in a 100 moles of solution:
C) Molarity of the HCl solution:
D) What volume of 32.0 M HCl would I need to make the 500 mL of solution?