CHEMISTRY 101
Hour Exam III
December 6, 2007
Adams/Denofrio
Name __________________________________
Signature ________________________________
T.A./Section ______________________________________
“It is in the ability to open our eyes and minds where limitless wonders are
discovered.”
This exam contains 17 questions on 7 numbered pages. Check now to make sure you have a
complete exam. You have one hour and fifteen minutes to complete the exam. Determine
the best answer to the first 15 questions and enter these on the special answer sheet. Also,
circle your responses in this exam booklet. Show all of your work and provide complete
answers to questions 16 and 17.
1-15
(30 pts.)
_________
16
(18 pts.)
_________
17
(12 pts.)
_________
(60 pts)
_________
Total
Useful Information:
1.000 L = 1000.0 mL
Always assume ideal behavior for gases (unless explicitly told otherwise).
PV = nRT
R = 0.08206 L·atm/mol·K
K = C + 273
STP = standard temperature and pressure = 0C and 1.00 atm
NA = 6.022 x 1023
Solubility Rules:
1. Most nitrate salts are soluble.
2. Most salts of sodium, potassium, and ammonium cations are soluble.
3. Most chloride salts are soluble. Exceptions: silver(I), lead(II), and mercury(I) chloride.
4. Most sulfate salts are soluble. Exceptions: calcium, barium, and lead (II) sulfate.
5. Most hydroxide salts can be considered insoluble. Soluble ones: sodium, potassium, and
calcium hydroxide.
6. Consider sulfide, carbonate, and phosphate salts to be insoluble. Soluble ones: sodium
and potassium.
CHEMISTRY 101
Hour Exam III
Fall 2007
Page No. 1
Consider the element sulfur to answer questions 1 – 2.
1. How many unpaired electrons does sulfur contain in its ground state?
a) 0
b) 1
c) 2
d) 3
e) 6
2. What is the correct electron configuration for the most stable form of the sulfur ion in an
ionic compound?
a)
b)
c)
d)
e)
1s22s22p6
1s22s22p63s2
1s22s22p63s23p2
1s22s22p63s23p4
1s22s22p63s23p6
---------------------------------------------------------------------------------------------------------------3. Why does elemental hydrogen exist as a diatomic molecule? Choose the best answer.
a) Each hydrogen atom wants to have a 1s2 electron configuration in order to have a
filled shell.
b) The hydrogen molecule must be more stable (at a lower energy state) than the
hydrogen atoms existing separately.
c) That is just how the Lewis structure works out.
d) The electron-electron repulsion between the separate atoms is so great that an electron
is transferred and an ionic bond forms.
e) The electronegativities between the two atoms are identical so naturally a single bond
forms.
4. How many of the following statements are true?
I. Energy can be defined as whatever is required to oppose a natural tendency.
II. Quantized energy is a continuous spectrum, like a ramp or the slope of a hill.
III. If energy is transferred into a system, the system works to transfer the energy back
out.
IV. If a process requires activation energy to proceed, the process must be endothermic
overall.
V. The driving force for a chemical reaction is to achieve a lower energy state.
a) 1
b) 2
c) 3
d) 4
e) 5
5. Can an electron in a phosphorus atom ever be in a 3d orbital? Choose the best answer.
a)
b)
c)
d)
Yes. An electron can be excited into a 3d orbital.
Yes. A ground-state electron in phosphorus is located in a 3d orbital.
No. Only transition metal atoms can have electrons located in the d orbitals.
No. This would not correspond to phosphorus’ electron arrangement in its ground
state.
e) Both c and d are correct.
CHEMISTRY 101
Hour Exam III
Fall 2007
Page No. 2
6. Which of the following elements has the largest atomic radius?
a) Ca
b) Al
c) N
d) Sr
e) F
7. Of the compounds listed below, which has octahedral geometry and is polar overall?
a)
b)
c)
d)
e)
SF6
I3–
ICl5
HCl
XeF4
8. Of the compounds listed below, which has at least one bond angle that is 90° around the
central atom?
a)
b)
c)
d)
e)
H2
ClF3
BF3
CH4
CO2
9. Which of the following bonds most likely resulted from actual electron transfers from one
atom to another causing an electrostatic attraction between the two newly formed ions?
a)
b)
c)
d)
e)
O–O
N–O
Si–O
C–O
Mg–O
10. Which has a smaller atomic radius, an atom of fluorine or an atom of lithium? Choose
the best answer.
a) They are the same size because their electrons are contained in the same principle
energy level.
b) An atom of lithium is smaller than an atom of fluorine because lithium has fewer
protons.
c) An atom of lithium is smaller than an atom of fluorine because as you add electrons
going across a row, the electron shells get further and further from the nucleus.
d) An atom of fluorine is smaller than an atom of lithium because with more protons the
electrons are pulled closer to the nucleus.
e) An atom of fluorine is smaller than an atom of lithium because fluorine has a high
ionization energy and will not lose electrons as easily as lithium.
CHEMISTRY 101
Hour Exam III
Fall 2007
Page No. 3
---------------------------------------------------------------------------------------------------------------Consider the following processes to answer questions 11 – 12.
I. A match burns after it is struck against a matchbox.
II. A pot of liquid water boils on the stove.
III. A banana freezes after it is submerged in liquid nitrogen.
IV. Solid CO2 (dry ice) sublimes into gaseous CO2.
11. Which of the following are exothermic processes?
a)
b)
c)
d)
e)
I, II
I, III
II, IV
I only
IV only
12. Choose the energy diagram that best represents process I: A match burns after it is struck
against a matchbox.
---------------------------------------------------------------------------------------------------------------------
CHEMISTRY 101
Hour Exam III
Fall 2007
Page No. 4
Consider the following compounds to answer questions 13 – 15.
CO2
N2
CCl4
PBr5
13. How many of the compounds above contain polar covalent bonds?
a) 0
b) 1
c) 2
d) 3
e) 4
14. How many of the compounds above are polar overall?
a) 0
b) 1
c) 2
d) 3
15. Which compound exhibits resonance?
a)
b)
c)
d)
e)
CO2
N2
CCl4
PBr5
At least two of the above compounds exhibit resonance.
e) 4
CHEMISTRY 101
Hour Exam III
Fall 2007
Page No. 5
16. The following are true/false questions that require explanation. State whether the
underlined statements are “true” or “false” and then provide the requested explanation or
support. Please limit your answers to the space provided.
True or False? Exciting a sample of neon gas (like we did in lecture) results in the
emission of white light.
 If true, thoroughly explain why white light is observed.
 If false, provide a thorough explanation.
True or False? The hydrogen 1s orbital and the lithium 1s orbital are the same size.
 If true, explain why.
 If false, state which 1s orbital should be larger along with an explanation.
CHEMISTRY 101
Hour Exam III
Fall 2007
Page No. 6
16. cont’d
True or False? Lithium, sodium, potassium, and rubidium are considered an
isoelectronic series because they all have the same number of valence electrons.
 If true, rank the atoms in order of increasing ionization energy and justify your
answer.
 If false, explain why and provide an isoelectronic series that contains at least four
atoms/ions. Then, rank the atoms/ions in your series in order of increasing
ionization energy and justify your answer.
CHEMISTRY 101
Hour Exam III
Fall 2007
Page No. 7
17. Consider the molecules HF and HCl.
a) Which of the two molecules contains a stronger polar bond? Explain your answer.
b) For which substance are the dipole-dipole interactions between the molecules
stronger? Explain your answer. Be sure to discuss how partial charges (charge
separation) play a role.
c) Starting with liquid HF and liquid HCl, as we heat these samples at the same rate,
which would boil first? Be sure to thoroughly explain your answer.