Practice Version
End of Year Chemistry Talent Show
Notes:
 The subject of chemistry explores the building blocks of the world. I wanted
you to truly experience chemistry & have fun while doing it. You spent a lot of
time out of your seat working directly with chemicals. This course was taught
in a building block fashion. I hope that you were able to gradually accumulate
knowledge & skills in an ever growing “toolbox” which demonstrated that as
chemistry got more complex……there was a dependence on a connected
web of fundamentals that allowed you to investigate the natural world at an
ever deepening level. This exercise is cumulative and allows you, in three
problems, to demonstrate a year of study.
 There are 110 raw points available. Your final score will be out of 175 points
based on the percentage of the 110 points that you earn.
 This exercise contains multi-part problems whereby the answer to one part of
the problem may depend on the answer to a previous part. I don’t believe it is
fair to experience “double jeopardy”. If you can’t 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 will still
earn full credit for that part.
 Take a deep breath & relax. Accept the fact now that you’re not going to know
everything and that you’re 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
& not getting stressed & 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’re 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.
 Show all your work on the paper provided.
 The following reference resources are provided on separate pages: periodic
table, valence table, solubility rules, & activity series. Additional reference info
is provided within this document.
Some Important Hydrocarbons
methane = CH4
glucose = C6H12O6
propane = C3H8
sucrose = C12H22O11
butane = C4H10
methanol = CH3OH
octane = C8H18
ethanol = C2H5OH
kerosene = C12H26
cellulose = C6H10O5
Problem I:
(51 pts)
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Tool Box
d = 0.789 g/mL
1 mile = 5280 ft
1.06 qt = 1 L
1 in = 2.54 cm
a) What type of compound is ethanol? Explain what holds this structure
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. (8 pts)
c) What is the molar mass of ethanol? What is the percent by mass of oxygen in
the compound? (4 pts)
d) Write a balanced equation for the combustion of ethanol in a car engine. (3 pts)
e) What makes this a chemical change rather than a physical change? (3 pts)
f) 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)
g) 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)
h) How many grams, counting units, and molecules of ethanol were burned to
fuel the trip? (6 pts)
i) How many molecules of carbon dioxide would be leaving the tailpipe of your
car during the trip? (3 pts)
j) Draw Lewis structures for the oxygen and carbon dioxide molecules. What is
similar about their structures & properties? (4 pts)
k) You like your car but you crave more speed. You decide to ditch your alcohol
fueled sports car for a nuclear powered model. The nuclear event is the
decay of plutonium. Write the nuclear equation for unstable Pu (mass 239) if it
breaks down by alpha decay. (2 pts)
l) The aluminum atoms that form your modern engine are reacting with oxygen
from the air to form aluminum oxide. Write a balanced equation for this
reaction. What type of reaction is it? (3 pts)
m) 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: (18 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:
Data Table
Object
Empty crucible and lid
Crucible, lid, and Hg
Crucible, lid, and compound
Chemistry I
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Mass (g)
23.117
25.608
27.362
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a) Calculate the empirical formula of the compound formed between mercury
and oxygen. (you 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) If the accepted value for the %Hg is 52.15%, what is the percent error for the
experiment? (2 pts)
d) Explain what would have been the effect on the %Hg if some of the
compound had been spilled before the final massing? (3 pts)
e) If we were to 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. What type of reaction is it? (3 pts)
Problem III: (41 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 in a bottle 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 the aluminum metal. (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 the total molecular & net ionic equations for the reaction. What type of
reaction is this? (5 pts)
d) Explain in detail what occurred during this chemical change. (4 pts)
e) Write electron configurations for aluminum before and after the reaction. What
happened to the aluminum atoms and why? (5 pts)
f) How many protons, neutrons, and electrons would be in the aluminum ion? (3 pts)
g) How many grams of zinc will be produced before the reaction runs out? (3 pts)
h) What causes the reaction to stop? (2 pts)
i) How many grams of the excess reactant will be left over when the reaction
stops? (4 pts)
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j) Write the total molecular equation for the second reaction. What type of
reaction is this? Write the total molecular equation for the loud final reaction.
What type of reaction is this? (3 pts)
k) Why should the student keep the bottle upside down during the collection
process? (1 pt)
l) Draw the Lewis structure for the water molecule. (2 pts)
m) Assume that from the first reaction you had a left over solution of aluminum
chloride. You you put crystals of plumbous nitrate into this solution and a white
solid forms. Write total molecular and net ionic equations for this reaction. (4 pts)
Chemistry I
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