“Quasi” Final Exam
Notes:
 Your final exam will count as 1/7 of your final grade in chemistry. Each
trimester counts 2/7.
 There will be 100 total points available on the exam. Your grade will be
determined by the percentage of those points that you earn.
 The exam will contain multi-part problems whereby the answer to one part of
the problem may depend on the answer to a previous part. If you can not
solve the previous part, then make up a reasonable answer that you can use
on the subsequent part. If you can show your work correctly using the
“estimated” answer, you can still earn full credit for that part.
 During a cumulative exam it is important that you relax. Accept the fact now
that you are probably not going to know everything and that you are going to
get something “wrong”. It will be OK! The key is to make your best showing by
getting all of them right that you do know and not getting rattled by the ones
that you don’t. When you get stuck or confused, skip that one and
concentrate on the ones that you immediately know how to solve or answer. If
you have time, come back to the others. You don’t want to spend 20 minutes
on one that you are not likely to earn points on anyway and then never get to
attempt four problems at the end of the test that you could have completed
easily.
Problem I:
(43 pts.)
Tool Box
Ethanol = C2H5OH
d = 0.789 g/mL
$1.12/gal
1 mile = 5280 ft
1 in = 2.54 cm
1.06 qt = 1 L
a) What type of compound is ethanol? Explain how it is held together? (4 pts.)
b) Write an electron configuration for each element in the ethanol molecule. Draw
a Lewis structure for ethanol. Explain the reasoning for the number of electrons
you assigned to the carbon, oxygen, and hydrogen atoms. (5 pts.)
c) What is the molar mass of ethanol? (1 pt.)
d) What is the percent by mass of carbon in the compound? (2 pts.)
e) Write a balanced equation for the combustion of ethanol. (3 pts.)
f) What makes this a chemical change rather than a physical change? (3 pts.)
g) It is now the year 2025 and gasoline powered cars are outlawed and the U.S.
has finally adopted the metric system. The speedometer in your ethanolpowered sports car says (and it really does talk to you) that you are traveling
at a rate of 94 Km/hr. How fast are you going in mph? (3 pts.)
h) Your car’s fuel efficiency using ethanol is 19.5 Km/L. If you travel 300. Km,
how many liters of ethanol have you burned? . (2 pts.)
i) How many grams, counting units, and molecules of ethanol were used? (6 pts.)
j) Draw Lewis structures for the oxygen and carbon dioxide molecules. What is
similar about their structures and properties? (5 pts.)
Chemistry I
Cary Academy
W.G. Rushin
1
k) The aluminum atoms that form your engine are reacting with oxygen to form
aluminum oxide. Write a balanced equation for this reaction. What type of
reaction is it? (3 pts.)
l) Salts like aluminum oxide are structurally different from ethanol. Compare and
contrast salts with molecules. What important differences exist between these
two classes of compounds? (6 pts.)
Problem II: (38 pts.)
A chemistry student obtains a chunk of aluminum and measures its mass on a
balance. The student pours some water in a graduated cylinder and reads the
volume. The chunk of metal is placed in the cylinder and the new volume is
recorded. The student masses out some zinc chloride and dissolves it in a flask
with water to make a solution. The aluminum is taken from the water and added
to the zinc chloride solution. Metallic crystals begin growing on the piece of
aluminum. The piece of aluminum dissolves and the flask seems to get warmer.
The student adds some hydrochloric acid to the flask and observes bubbles
being produced. The bubbles are collected and a lit match yields a loud and fiery
reaction.
Data Table
Measurement
Reading
Mass of the aluminum piece
3.933 g
Initial volume of the water
23.7 mL
Final volume of the water
25.4 mL
Mass of zinc chloride
27.554 g
Observations: The aluminum piece begins to darken and then metallic looking
crystals begin to grow from its surface. The solution remains clear but gets
warmer. When acid is added, the metallic crystals begin to dissolve and bubbles
rise to the surface. The flask gets much warmer.
a) From the data, determine the density of aluminum. (3 pts.)
b) If the literature value for the density of aluminum is 2.70 g/mL, what is the
student’s percent error for the experiment? (2 pts.)
c) Write a total molecular equation for the reaction. (3 pts.)
d) Write a net ionic equation for the reaction. (3 pts.)
e) Explain in detail what occurred during this chemical change. (4 pts.)
f) What type of reaction is this? (1 pt.)
g) Write electron configurations for aluminum before and after the reaction. What
happened to the aluminum atoms and why? (5 pts.)
h) How many protons, neutrons, and electrons would be in the aluminum ion?
(3 pts.)
i) Why should the student keep the plastic bottle upside down during the
collection process? (2 pts.)
j) Write the total molecular equation for the last reaction. What type of reaction
is this? (3 pts.)
k) Draw the Lewis structure for the water molecule. (2 pts.)
Chemistry I
Cary Academy
W.G. Rushin
2
l) Assume that from the first reaction you had a left over solution of aluminum
chloride. Explain what you would observe if you put crystals of plumbous nitrate
into this solution. (3 pts.)
m) Write total molecular and net ionic equations for this reaction. (4 pts.)
Problem III: (19 pts.)
A sample of mercury is placed in a crucible and heated in the presence of air to
synthesize an oxide compound. The following experimental data was obtained:
Object
Empty crucible and lid
Crucible, lid, and Hg
Crucible, lid, and compound
Mass (g)
23.117
25.608
27.362
a) Calculate the empirical formula of the compound formed between mercury
and oxygen. (Do not have to show me how to calculate masses) (6 pts.)
b) Calculate the percent by mass of Hg in the compound using the measured
masses. (2 pts.)
c) Explain what would have been the effect on the %Hg if some of the
compound had been spilled before the final massing? (3 pts.)
d) If the accepted value for the %Hg is 52.15%, what is the percent error for the
experiment? (2 pts.)
e) If we decompose this compound, describe a test we can perform to confirm
the presence of pure oxygen. (2 pts.)
f) Write a balanced equation for this test. (3 pts.)
g) What type of reaction is it? (1 pt.)
Chemistry I
Cary Academy
W.G. Rushin
3