Honors Chemistry- Chapter 8 Exam
Bartelt 2013
DO NOT WRITE ON THIS EXAM!!
Version A
(3pts each)
1. One mole of something consists of ________________ units of that substance.
a) 12.01
b)
1.008
c) 1.66 x 10-24
d) 6.022 x 1023
e) 32.00
2. True or false? The empirical formula and the molecular formula for a compound cannot be the same.
a) True
b) False
3. Which represents the greatest mass?
a) 1.0 mol Si
b) 1.0 mol Zn
c) 1.0 mol As
d) 1.0 mol Co
e) all the same
4. You have two beakers on your lab table. Beaker #1 contains 32.06g of sulfur and Beaker #2 contains 74.92g of arsenic (As). Which beaker
contains the greatest number of atoms? Choose the best answer.
a) Beaker #1 because one sulfur atom weighs less than one arsenic atom so you need more of the sulfur atoms to fill the beaker.
b) Beaker #1 because it contains more moles of sulfur atoms than the number of moles of arsenic atoms in Beaker #2.
c) Beaker #2 because arsenic has a greater mass than sulfur
d) Beaker #2 because it contains more moles of arsenic atoms than the number of moles of sulfur atoms in Beaker #1.
e) Beakers #1 and #2 contain the same number of atoms because there is one mole in each.
5. A sample with 3.31 x 1024 atoms of copper contains how many moles of copper?
a) 1.99 x 1048 mol
b) 3.49 x 102 mol
c) 8.65 x 10-2 mol
d) 1.82 x 10-1 mol
e) 5.50 mol
6. Uranium hexafluoride is a chemical compound essential to the enrichment of uranium. Scientists working on the Manhatan Project (the effort to
develop the first atomic bomb in the United States) used this compound to separate Uranium-235 from Uranium 238. It was determined that
exactly 3.31 x 1024 molecules of uranium hexafluoride would need to be purified to reach critical mass (the mass required for a self-sustaining
nuclear reaction). How many moles of uranium hexafluoride are needed?
a) 1.99 x 1048 mol
b) 3.49 x 102 mol
c) 8.65 x 10-2 mol
d) 1.82 x 10-1 mol
e) 5.50 mol
7. Which of the following contains the smallest number of atoms?
a) 1.0 g Br
b) 1.0 g P
c) 1.0 g Al
d) 1.0 g U
e) 1.0 g Na
8. The molar mass of Al(OH)3
a) 78.01 g/mol
b) 43.99 g/mol
d) 46.00 g/mol
e) 51.02 g/mol
c) 75.99 g/mol
9. How many moles of phosphorus are in 9.105g of phosphorus?
a) 0.2930 mol
b) 0.2940 mol
c) 282.0 mol
d) 5.48 x 1024 mol
e) 1.770 mol
10. A sample contains 1.807 x 1024 atoms of sodium. What is the mass in grams of the sample?
a) 68.99g
b) 32.07g
c) 22.99g
d) 7.860 x 1022 g
11. A sample of ammonia (NH3) has a mass of 45.5 g. How many molecules are in this sample?
a) 2.67 molecules b) 2.74 x 10 25 molecules
c) 2.25 x 1023 molecules
d) 1.61 x 1024 molecules
e) none of these
e) 9.02 x 10–16 molecules
12.
The empirical formula of styrene is CH; its molar mass is 104.1 g/mol. What is the molecular formula of styrene?
a) C2H4
b) C8H8
c) C10H12
d) C6H6
e) none of these
13.
A gaseous compound containing only carbon and hydrogen was analyzed and found to consist of 16.35% hydrogen. What is the empirical
formula of the compound?
a) CH2
b) C3H7
c) CH3
d) C7H16
e) CH
14.
Which compound contains the highest percent by mass of hydrogen?
a) HCl
b) H2O
c) H2SO4
d) H2S
e) HF
Ammonium sulfate, (NH4)2SO4, contains what percent nitrogen by mass?
a) 42.4%
b) 10.6%
c) 21.2%
d) 13.7%
e) none of these
15.
16. Which of the following has the empirical formula CH2?
a) C2H6
b) H2CO3
c) C6H6
d) C6H12
e) C2H4O
17. Determine the mass of cobalt that has the same number of atoms as a 2.24g sample of iron (Fe).
I) 0.040 g Co
II) 2.24 g Co
III) 2.36 g Co
IV) 2.41g Co
V) 4.09 x 1023g Co
Which three of the answer choices above can be eliminated IMMEDIATELY with virtually no thought because they’re not even close.
a) I, II, and III
b) II, III, and IV
c) II, III and IV
d) I, IV and V
e) I, II, and V
Short Answer
Show ALL work for credit. Use proper units and sig figs. BOX ALL FINAL ANSWERS.
1.
Calculate the molecular formula of a compound that is 60.00% carbon, 4.48% hydrogen, and 35.53% oxygen. The molar
mass of the molecular formula is between 540g/mol. (11 points)
C9H8O4
C27H24O12
2.
For the following reaction, predict the product(s) formed. If you have 3.4x10 22 molecules of the product formed, how many
grams of product do you have? (10 points)
Li + Cl2  _______
LiCl 2.4g
3.
You begin the lab with 100g of hydrate, ZnSO4 * x H2O. Upon heating, 43.86g of water are released, leaving only the
anhydrous salt behind. How many grams of the anhydrous salt are formed? How many molecules? (10 points)
.348 mol ZnSO4
2.43 mol H2O
x=7
EXTRA CREDIT: (NO PARTIAL CREDIT) (+5 points)
Fifteen grams of a hydrate is heated and 7.05g of water is released. The anhydrous salt is determined to be sodium sulfate. What is the
empirical formula of the hydrate?