Department of
Chemistry, Geosciences, and Environmental Science
Chemistry
1054-010 College
Chemistry Fall
2006
Exam 4-A-Key
Name:_______________________________________________________
(Please write your name legibly)
Read all directions and questions carefully!! This exam consists of two parts. The first part consists of 10 multiple choice questions worth four points each for a total of 40 points. The second part consists of five numerical problems worth either 10 or 15 points per question for a total of 60 points. Show all your work necessary for the numerical problems as partial credit will be given for those problems.
Possibly Useful Constants
Score
Part 1 (40 points):_____________________
Part 2 (60 points):_____________________
Total (100 points):_____________________
Don’t forget to put your
name on this test!
Good Luck!!
Part 1
Multiple Choice
Please indicate the answer to each question by putting your choice in the space provided. There is only one correct answer for each question. There will be 10 multiple choice questions worth 4 points each.
1. The electron domain geometry associated with 5 electron domains is:
(a) linear (c) octahedral
(b) trigonal planar (d) tetrahedral
(e) trigonal bipyramidal
Answer: E
Refer to table 9.2 on page 349 in your book.
2. The molecular geometry associated with 4 bonding domains and 2 nonbonding domains is:
(a) octahedral (d) seesaw
(b) T-shaped (e) trigonal bipyramidal
(c) square pyramidal (f) square planar
Answer: F
Refer to table 9.3 on page 354 in your book.
3. Which hybrid orbitals are associated with a tetrahedral geometry?
(a) sp (c) dsp3
(b)
sp2 (d) d2sp3
(e) sp3
Answer: E
Refer to table 9.4 on page 366 in your book.
4. There are ________s bonds and ________p bonds in the molecule shown above.
(a) 4, 2 (c) 6, 4
(b) 2, 2 (d) 2, 6
(e) 6, 2
Answer: E
Each single, double, or triple bond contains
1 s
bond. Each double bond contains 1 p bond
and each double bond contains 2 p bonds.
5. A gas originally at 27°C and 1.00 atm pressure occupies a volume of 3.9 L. The gas is then cooled at constant pressure to 11°C. What is the new volume of the gas?
(a) 0.27 L (c) 3.9 L
(b) 3.7 L (d) 4.1 L
(e) 0.24 L
Answer: B
Using Charles’ Law: 
. Remember to convert the temperatures to Kelvin first.
6. Which one of the following gases will have the fastest rate of diffusion at the same temperature and pressure?
(a) He (c) N2
(b) CO2 (d) O2
(e) All gases have the same rate of diffusion at the same temperature and pressure.
Answer: A
The gas with the smallest molar mass will
have the fastest rate of diffusion.
7. A real gas behaves most like an ideal gas under conditions of:
(a) high pressure and low temperature (c) low pressure and low temperature
(b) high pressure and high temperature (d) low pressure and high temperature
Answer: D
8. A solid material that does not conduct electricity but becomes a conductor when melted is a(n):
(a) metallic solid (c) network covalent solid
(b) covalent solid (d) ionic solid
Answer: D
9. Ion-dipole forces play a major role in which of the following species?
(a) NH3(g) (c) H2O(l)
(b) NaCl(aq) (d) NaCl(s)
(e) I2(s)
Answer: B
10. A phase diagram for a particular substance is shown in the diagram above. The critical point is designated by which letter?
(a) a (c) c
(b) b (d) d
(e) e
Answer: E
Part 2
Numerical Problems
Solve the following problems, keeping track of significant figures where applicable. Please show all the work necessary to obtain your answer in order to receive partial credit for possibly wrong answers. Generally, full credit will not be given for the correct answer without any of the work performed to obtain the answer being shown on the paper. Each question is worth either 10 or 15 points.
11. (10 points) What is the pressure exerted by 1.354 g of CO(g) occupying a volume of 675 mL at a temperature of 35°C?
Use the ideal
gas law: PV = nRT;
Making the
necessary conversions: 
Calculate moles
of CO(g): 
Solving the
ideal gas law for P: 
12. (15 points) Potassium chlorate, KClO3(s), decomposes upon heating to potassium chloride and oxygen gas according to the reaction:
2 KClO3(g) ¾¾® 2 KCl(s) + 3 O2(g)
Suppose a mixture containing KClO3(s) was decomposed to produce 294 mL of O2(g) which was collected over water at a total pressure of 715 torr and a temperature of 21°C. Given a vapor pressure of water of 18.65 torr at 21°C, calculate how many grams of KClO3(s) decomposed.
Gas stoichiometry problem:
known: 294 mL
of O2(g) collected over water at 715 torr and 21°C
unknown: ?? g KClO3
Calculate how
many moles of O2 were produced using the ideal gas law. First, calculate the partial pressure of
oxygen by subtracting the vapor pressure from the total pressure:
Make the
necessary unit conversions before using the ideal gas law:
Calculate the
number of moles of O2:
Convert to moles
of KClO3 using the balanced chemical equation:
Convert to grams
of KClO3:
Grams of KClO3 = 0.00744 mol(122.6 g/mol)= 0.913 g (3 sig figs)
(5 points extra credit, no partial credit) Suppose the mass of the entire mixture containing KClO3 was 1.42 g. What is the %KClO3 in the mixture?
13. (10 points) Some of the terms and materials discussed in the modern materials chapter (Chapter 12) are listed below. Please match up the appropriate terms with the statements below them by placing the letter of the correct choice next to each term. Not every choice will be used.
A. conductors B. semiconductors C. insulators
D. superconductor E. ceramics F. addition polymers
G. thermoplastic polymers H. thermosetting polymers I. elastomers
J. vulcanization K. condensation polymers
L. nematic liquid crystalline phase M. smectic liquid crystalline phase
N. cholestic liquid crystalline phase O. n-type semiconductor
P. p-type semiconductor Q. biomaterial
S. nanomaterial
B A liquid crystal in which the molecules are aligned in a particular direction but with no other order between the moleculares
F A polymer such as polyethylene.
D A substance with no electrical resistance.
A A solid material with no band gap between the valence and the conduction bands.
S Includes very small material such as carbon nanotubes which can be used as semiconductors or conductors.
H A plastic that is shaped initially by a chemical process and cannot be reshaped by heating.
E These materials are known for their hardness and their resistance to heat. Some of them exhibit high temperature superconductivity.
I A plastic that behaves like a rubber band.
O A semiconducting material that is doped with small amounts of an atom with more valence electrons, such as silicon doped with phosphorus.
Q Materials such as “smart” sutures which automatically tighten when exposed to the body’s temperature are examples of this type of material.
14. (10 points) A solution is prepared by dissolving 14.25 g of ethanol, C2H5OH, in 126.4 g of water. What is the mass percent and the mole fraction of ethanol in this solution?
Mass percent is
defined as 
Calculate moles
of each component in advance of calculating mole fraction:
Mole fraction is
defined as: 
15. (15 points) Give the electron domain geometry, the molecular geometry, the ideal bond angle(s) and the hybridization on the central atom for the following Lewis structures. From the geometry, determine whether the molecule is polar or not.
|
Lewis Structure |
Electron Domain Geometry |
Molecular Geometry |
Ideal Bond Angle(s) |
Hybridization on central atom |
Is the molecule polar or not? (Yes or No) |
|
|
trigonal planar |
bent |
120° |
sp2 |
NO |
|
|
trigonal planar |
trigonal planar |
120° |
sp2 |
NO |
|
|
trigonal bipyramidal |
seesaw |
90° and 120° |
dsp3 or sp3d |
YES |
