CHEMISTRY 101
Hour Exam III
December 3, 2009
Adams/Sperling
Name ___________________________________
Signature ________________________________
Section ______________________________________
"Let me tell you the secret that has led me to my goal. My strength lies
solely in my tenacity."
-Louis Pasteur-
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
(12 pts.)
_________
17
(18 pts.)
_________
(60 pts)
_________
Total
CHEMISTRY 101
Hour Exam III
Fall 2009
Page No. 1
1. Which of the following electron configurations is incorrect?
a)
b)
c)
d)
e)
Cl–: [Ar]
Ti: [Ar] 4s23d2
I: [Kr] 5s25d105p5
N: [He] 2s22p23s1
At least two of the above have incorrect electron configurations.
2. How can a chemical reaction be exothermic overall if activation energy (an endothermic
component) is required? Choose the best answer.
a) A lot more energy could be released in making the products than what was required
to get the reaction started.
b) The reaction could end up being less stable overall which is why activation energy is
required in the first place. An exothermic reaction would help accomplish this less
stable state.
c) If energy is transferred into a chemical system (like activation energy), the system
works to transfer the energy back out so that the energies “balance”.
d) If the overall potential energy of the reaction is higher than the initial state, then the
reaction can be exothermic overall.
e) It is impossible to have exothermic reactions overall if activation energy is required.
3. Ernest Rutherford’s experiment supported that the atom contains a positively-charged
nucleus. Why then does our data show that the electrons are not all crashing into the
nucleus? Choose the best answer.
a) Electrons are also positively charged and like charges repel one another.
b) Electrons must all have the same spin and this cannot be accomplished if they are all
located on the nucleus.
c) Electrons only exist in their excited states but if a ground state were possible, then
they would be located on the nucleus.
d) Electrons only exist in certain energy levels both in the ground state and excited state.
e) All of the above explain why the electrons are not all crashing into the nucleus.
4. Arrange the following bonds from the least polar to the most polar bond.
C–F, Na–F, Ge–F, Si–F
a)
b)
c)
d)
e)
C–F < Ge–F < Si–F < Na–F
Si–F < C–F < Ge–F < Na–F
C–F < Si–F < Ge–F < Na–F
Na–F < Ge–F < Si–F < C–F
Na–F < C–F < Si–F < Ge–F
CHEMISTRY 101
Hour Exam III
Fall 2009
Page No. 2
---------------------------------------------------------------------------------------------------------------Consider the following atoms/ions to answer questions 5 – 7.
K+, Ca2+, Pb, F, Rn
5. How many atoms/ions contain at least one unpaired electron in its ground state?
a) 1
b) 2
c) 3
d) 4
e) 5
6. Arrange the atoms/ions in order of increasing size.
a)
b)
c)
d)
e)
F < Ca2+ < K+ < Pb < Rn
F < K+ < Ca2+ < Rn < Pb
F < K+ < Ca2+ < Pb < Rn
Pb < Rn < K+ < Ca2+ < F
F < Ca2+ < K+ < Rn < Pb
7. How many of the atoms/ions have the same number of valence electrons?
a) 1
b) 2
c) 3
d) 4
e) 5
--------------------------------------------------------------------------------------------------------------------8. Which of the following statements is false concerning orbitals?
a) An orbital is a region of space where an electron might be found with 90%
probability.
b) As an electron absorbs more energy, the orbital in which it might be found becomes
larger and/or more complex.
c) For each successive energy level, a new type of orbital is added.
d) For each orbital, an electron orbits the nucleus around the outer edge according to the
shape of that orbital.
e) The d orbitals begin at the third principal energy level and can hold a maximum of 10
electrons for a given energy level.
9. Which of the following is true regarding the “pop bottle” reaction where hydrogen gas
and oxygen gas react to form water?
a) This is an endothermic reaction overall since the hydrogen and oxygen must be put
into the Bunsen burner to get them to react.
b) The average bond energies for water are greater than the average bond energies for
hydrogen and oxygen.
c) The reactants (hydrogen and oxygen) are more stable than the products (water).
d) All of the above (a–c) are true.
e) All of the above are false.
CHEMISTRY 101
Hour Exam III
Fall 2009
Page No. 3
---------------------------------------------------------------------------------------------------------------Consider the following species to answer questions 10 – 12.
BeH2
ClO3–
TeF4
SeO2
10. How many of the compounds above have a linear shape?
a) 0
b) 1
c) 2
d) 3
e) 4
11. How many of the compounds above have at least one bond angle that is 120°?
a) 0
b) 1
c) 2
d) 3
e) 4
12. How many of the compounds above are polar overall?
a) 0
b) 1
c) 2
d) 3
e) 4
--------------------------------------------------------------------------------------------------------------------13. Recall in both lecture and lab when you saw different colors produced by various salts in a
flame. Each salt produced its own characteristically colored flame. Which of the following
statements is/are true regarding how this process works?
I. To return to the ground state, the electrons had to release a specific amount of energy
since they only exist in certain energy levels and never in-between.
II. The electrons were excited to higher energy levels located further from the nucleus
and were unstable.
III. The released energy corresponds to a certain wavelength of light which corresponds
to a specific color.
IV. Each metal ion has its own characteristic color because they each have different
electron arrangements.
V. Heat was added to each salt to excite the electrons in the metal ions.
a)
b)
c)
d)
e)
I only
I and III
II and III
I, II, and III
All of the statements are true regarding how this process works.
14. Which of the following compounds exhibits ionic bonding?
a)
b)
c)
d)
e)
CaCl2
CH4
PCl3
F2
HF
CHEMISTRY 101
Hour Exam III
Fall 2009
Page No. 4
15. For a hydrogen fluoride molecule, which of the following statements is false about the
bond between hydrogen and fluorine, H–F?
a) The bond between hydrogen and fluorine is very strong due to hydrogen bonding
interactions.
b) The electrons are more likely to be found around fluorine than hydrogen since
fluorine is more electronegative.
c) The arrow of the dipole moment is moving toward fluorine with fluorine having the
partial negative charge (δ–) and hydrogen having the partial positive charge (δ+).
d) The bond between hydrogen and fluorine is polar covalent because they share
electrons unequally.
e) All of the above statements are true about the bond between hydrogen and fluorine.
CHEMISTRY 101
Hour Exam III
Fall 2009
Page No. 5
16. The following are true/false statements that require explanation. State whether each are
“true” or “false” and then provide the requested explanation or support. Please limit
your answers to the space provided.
True or False? The boiling of water is an exothermic process since steam is created.
(Assume that the water is your system.) Whether true or false, provide a thorough
explanation along with a sketch or diagram to support your answer.
---------------------------------------------------------------------------------------------------------------True or False? CH3CH2CH3 (propane) is more likely to be soluble in water than soluble
in CCl4 due to the hydrogen bonding between propane and water. Whether true or false,
provide a thorough explanation to support your answer.
---------------------------------------------------------------------------------------------------------------True or False? It takes more energy to remove the first electron from strontium than the
second electron because strontium wants to become Sr2+ and have a noble gas
configuration. Whether true or false, provide a thorough explanation to support your
answer.
CHEMISTRY 101
Hour Exam III
Fall 2009
Page No. 6
17. Examine the following pairs of molecules. Predict and explain which molecule will have
a higher boiling point. Include the Lewis structure of each covalently-bonded molecule
in your explanation along with a discussion of polarity and intermolecular forces. (It is
not necessary to show resonance structures where applicable.)
Only complete and coherent explanations will receive full credit. Please limit your
answers to the space provided.
a) CO2 and SO2
b) XeF4 and XeF2
CHEMISTRY 101
Hour Exam III
c) FeCl3 and PCl3
d) CH3CH2OH and CH3OCH3
Fall 2009
Page No. 7