PRACTICE EXAM 1-A
CHEMISTRY E-1ax
LAST NAME: ________________________________________
FIRST NAME: ________________________________________
You should give yourself 2 hours to complete this exam
NOTES:
1. This exam has 6 pages with 6 problems, plus the cover sheet, useful information,
periodic table, and scrap paper.
2. Note the point values of each exam question, and consider where you can best spend
your time.
3. Answer all questions on the exam sheets. Put your final answers in the boxes
provided. If you must use the back, then please indicate that clearly!
4. Do not use red pen!
5. For full credit, show all calculations; this also helps us award partial credit.
6. All numerical answers must include correct units for full credit.
1. ____________
2. ____________
3. ____________
4. ____________
5. ____________
6. ____________
TOTAL: ___________ / 100
1
1.
For this problem you will need to use numerical constants and conversion factors from
the Useful Information page. In addition, you will need atomic masses from the periodic
table.
Chrysoberyl is a hard yellow-green gemstone that consists of beryllium aluminate,
BeAl2O4. The world’s largest cut (faceted) chrysoberyl is 66.0 carats and is in the
collection of the Smithsonian Institute in Washington, D.C.
a)
Determine the molar mass, in units of g/mol, of BeAl2O4. (4 pts)
molar mass =
b)
Determine the number of electrons contained in 66.0 carats of BeAl2O4. (6 pts)
# of electrons =
c)
electrons
BeAl2O4 has a density of 3.7 g/mL. Determine the volume in cubic inches of 66.0 carats
of BeAl2O4. (6 pts)
volume =
1
g/mol
in3
( ______ / 16 pts)
2
2.
Aqueous sulfuric acid and aqueous barium hydroxide will undergo a reaction that is both
an acid/base reaction and a precipitation reaction, forming the insoluble salt barium sulfate.
a)
Write a complete, balanced equation for the reaction between aqueous sulfuric acid and
aqueous barium hydroxide. (Please include state symbols such as (s), (aq), etc.) (4 pts)
b)
Write a balanced net-ionic equation for the reaction between aqueous sulfuric acid and
aqueous barium hydroxide. (Please include state symbols such as (s), (aq), etc.) (4 pts)
c)
You are given 10.0 mL of H2SO4 solution of unknown concentration. You titrate this sulfuric
acid solution with 0.0100 M Ba(OH)2. The endpoint of the titration is reached when 31.2 mL
of the Ba(OH)2 solution have been added. During the course of the titration, the solution
turns increasingly cloudy due to the formation of the BaSO4 precipitate.
i)
How would you classify a solution of H2SO4? (1 pt)
(circle)
ii)
(circle)
iii)
electrolyte
non-electrolyte
As barium hydroxide is added to this sulfuric acid solution during the titration, what
would you expect would happen to the conductivity of the solution?
The conductivity of the solution will: (1 pt)
increase
decrease
remain the same
Determine the molar concentration of sulfuric acid in the original H2SO4 solution of
unknown concentration. (6 pts)
concentration of H2SO4 =
2
( ______ / 16 pts)
3
3.
Trimesic acid, which is used in the production of epoxies, plastics, and synthetic fibers,
contains only the elements C, H, and O.
a)
When 5.00 grams of trimesic acid are completely combusted in excess oxygen, 9.42 g of
CO2 and 1.29 g of H2O are collected. Determine the empirical formula of trimesic acid.
(10 pts)
empirical formula:
b)
The molar mass of trimesic acid is approximately 210 g/mol. Determine the molecular
formula of trimesic acid. (4 pts)
molecular formula:
c)
3
Write a complete, balanced equation for the combustion of solid trimesic acid.
(Please include state symbols such as (s), (aq), etc.) (4 pts)
( ______ / 18 pts)
4
4.
a)
Write the chemical formula for each of the following species. (1 pt each)
Phosphorous Pentachloride
Bromine
Lithium Peroxide
Ammonium Carbonate
Phosphoric Acid
Cupric Oxide
b)
Write an acceptable chemical name for each of the following. (1 pt each)
SO3
SO32–
Fe(SCN)3
c)
Write the oxidation state of each atom in the box above the atom. (1 pt per box)
Hg2I2
4
KO2
OF
CuSO4
( ______ / 18 pts)
5
5.
The following three solutions are mixed together (the order of mixing doesn’t matter):
200.0 mL of 0.200-molar sodium iodide, NaI
100.0 mL of 0.250-molar lead (II) nitrate, Pb(NO3)2
100.0 mL of 0.150-molar calcium iodide, CaI2
A bright yellow precipitate of lead (II) iodide, PbI2, is formed.
a)
Write a balanced net-ionic equation for this chemical reaction. Please include state
symbols such as (s), (aq), etc. (Hint: There is only one net-ionic reaction that occurs;
you should balance it with smallest whole-number coefficients.) (4 pts)
b)
Calculate the molar concentration of the Pb2+, I–, and NO3– ions in the resulting
solution, and determine the mass of lead iodide that is formed. (12 pts)
Pb2+ :
I– :
NO3– :
mass of PbI2 =
5
( ______ / 16 pts)
6
6.
Zinc and aluminum will each react with hydrochloric acid, HCl, to form their chloride
salts (ZnCl2 and AlCl3, respectively) and hydrogen gas.
You are given 5.00 grams of a mixture of zinc and aluminum. You react the mixture with
excess hydrochloric acid and collect all of the hydrogen gas evolved. You then mix the
hydrogen gas with excess oxygen gas and combust the mixture. All of the water resulting
from combustion is collected, and it weighs 2.36 grams. Determine the mass of zinc and
the mass of aluminum in the original mixture. (16 pts)
mass of Zn =
mass of Al =
6
( ______ / 16 pts)
Useful Information
Avogadro’s Number = 6.022 ! 1023
Density of water at 25°C = 1.00 g/mL
Unit Conversions:
1 gram = 5 carats
1 mL = 1 cm3
1 foot = 12 inches
1 inch = 2.54 cm
1 pound = 453.6 grams
Scrap Paper
Nothing on this page will be graded unless you clearly indicate
on a specific problem that additional work is located here.