Name:____________________ ChemTeam:_________________
Student Number:______________________
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Chemistry 1001 Spring 2004
HW#5 Due Thursday, May 5 at 5 pm (No extensions!)
Help Session: Sunday, May 1 at 5 pm Choppin Lobby.
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We continue to drill you on molecular shape/polarity problems! It
matters for Chem 1002, which is the reward course for surviving Chem
1001. Hey, no good deed goes unpunished! Seriously, Chem 1002 is a
great course, and you’re ready for it.
1. (Based on Question 6.37b, p. 178)
Draw the Lewis structure for HOF and describe the electron pair geometry and molecular
geometry.
2. (Based on Question 6.41b, p. 178)
Freon 12, CCl2F2, is a molecule in which two chlorines and two fluorines are attached to a
central carbon. Of course, it is tetrahedral, like this:
Which are the most polar bonds in this molecule, the C-F or the C-Cl?
Is the molecule polar overall?
Take pity on us: print neatly. Thanks--the graders.
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Name:____________________ ChemTeam:_________________
Student Number:______________________
3. (Based on Self Test 7B, #10, p. 198)
Considering the shape of the common solvent, carbon tetrachloride, CCl4, do you expect it
to be soluble in water? Explain your answer. If you can’t decide, Lewis structures may
help.
4. (Based on Self Test 7C #1, p. 206)
Describe the amount of motion exhibited by solids at room temperature.
5. (Weird version of Question 10, p. 212)
Molecules of a perfume can be detected a distance from the person wearing the perfume.
Draw a picture showing two people standing about five feet apart (stick people are OK)
and sketch the path by which the perfume molecules get from one person to the other.
You can assume the people are surrounded by air.
6. (Based on Question 36, p. 212)
Explain why a normal metal conducts better when it is cold than when it is hot. Can you
think of any practical applications of this behavior?
Take pity on us: print neatly. Thanks--the graders.
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Name:____________________ ChemTeam:_________________
Student Number:______________________
7. (Based on Exercise 8.6, p. 241)
How many moles of chromium (III) oxide, Cr2O3, can be made by the combination of
1 mol of chromium metal with a large excess of oxygen? Write the balanced reaction
before you answer the question.
________mol Cr2O3
8. (Based on Self test 8A #5e, p. 222)
In photosynthesis, carbon dioxide combines with water to form oxygen and the simple
sugar, glucose (C6H12O6). What mass in grams of CO2 is needed to make 4 pounds of
glucose? You must balance the reaction below first.
_________CO2 + _________H2O
 _________C6H12O6 + _________O2
___________g CO2
Take pity on us: print neatly. Thanks--the graders.
Page 3
Name:____________________ ChemTeam:_________________
Student Number:______________________
9. (Based on Self Test 8B, #4, p. 232)
What is the name we give to a material that changes the rate of a reaction without altering
the equilibrium of that reaction?
___________________
10. (Based on Lecture)
If a material of the type described in the previous problem is a protein from a biological
system, we call it an
_________________
11. (Based on Self Test 8D, p. 242)
Consider the electrolysis of water:
2H2O  2H2 + O2.
How many grams of oxygen can be produced from 36 grams of water?
_________g O2
12. (Based on Question 16e, p. 243)
How many carbon atoms are in 0.02 mol of butane, C4H10?
Take pity on us: print neatly. Thanks--the graders.
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Name:____________________ ChemTeam:_________________
Student Number:______________________
13. (Based on Question 20, p. 244)
Temperature generally increases the rate of reactions. Explain why.
14. (Based on Problem 8, Ch 5)
A sample of corn containing 1.00 gram is taken from a sealed tomb. A carbon-14 count of
38,250 disintegrations is detected over a period 10,000 minutes (approx 1 week). What is
the age of this sample in years, assuming a normal activity of 15.3 disintegrations per gram
per minute for fresh plant matter and a half-life of 5730 years?
15. (Based on previous problem, only harder). OK, the previous problem was contrived
to give us exactly an integer number of half-lives. Real samples don't do that. Suppose an
apparently older tomb is opened and this time we get a carbon-14 count of 16,907
disintegrations in a 10,000 minute period. Can you the age of that sample in years?
Take pity on us: print neatly. Thanks--the graders.
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Name:____________________ ChemTeam:_________________
Student Number:______________________
16. (Based on Problem 12, Ch. 5) Carbon is about 0.4% of your body mass. About how
many radioactive disintegrations do you emit per minute, using the assumptions about
radioactive carbon dating stated in the previous problems? (Be sure to state clearly your
weight--we need that to see if you did the problem right!).
17. (like Ch. 9 Q18)
The choice containing only basic compounds is:
a. CO2, HCl, Mg(OH)2, NaOH
b. HF, NaF, CO, H2S
c. NaOH, KOH, Al2O3
d. SO2, H2O, BaO
e. None--all of these contain at least one acidic compound
18. (like Ch. 9 Q33)
Which is the stronger acid and why? H3PO4 or H2PO4- ???
19. If pH goes up by 3 units (e.g., from pH 2 to pH 5 or from pH 6 to pH 9) the H3O+
concentration goes:
a. up by 1000
b. down by 1000
c. up by 100
d. down by 100
e. insufficient information
Take pity on us: print neatly. Thanks--the graders.
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Name:____________________ ChemTeam:_________________
Student Number:______________________
20. (like Ch. 9 P4) How many grams of solute are required to prepare 85 mL of 0.45 M
H3PO4?
3710
1670
3.71
1.67
1.82
21. (like Ch. 9 P10) What is the final concentration if 35 mL of 4.15 M KOH is diluted to
a new final volume of 100 mL?
3.83 M
1.453 M
2.35 M
1.23 M
4.7 M
22. (based on lecture) Which of the following statements is absolutely true?
a. Oxidation can be recognized as gain of electrons, loss of hydrogen or addition of
oxygen.
b. Oxidation can be recognized as loss of electrons, loss of hydrogen or addition of any
strongly electronegative element, including oxygen.
c. Reduction can be recognized as gain of electrons, addition of oxygen, or addition of
hydrogen.
d. Reduction can be recognized as gain of any electronegative element, including oxygen,
or addition of hydrogen.
e. This semantics stuff just drives me nuts--why again am I an English major?
Take pity on us: print neatly. Thanks--the graders.
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Name:____________________ ChemTeam:_________________
Student Number:______________________
23. (based on Ch. 10, Q20) In the following reaction, identify all the atoms that got
reduced. (Hint: don't think about it too hard).
Fe2O3 + 3 C  2Fe + 3 CO
24. (based on Ch. 10, Q29) How is the oxide of aluminum different from the oxide of
iron?
25. (based on Ch. 10, Q42) Besides electricity, what do the fuel cells used on the space
shuttle produce?
Take pity on us: print neatly. Thanks--the graders.
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