CHM 1010
FALL 2008
NAME ________________________________
GAGE
I.
EXAM 3
DATE: NOVEMBER 21, 2008
Select the best answer from the choices provided. Place your answer on the line in from of the question number.
_____ 1.
Which of the following elements is most likely to display dsp 3 hybridization? a. oxygen b. nitrogen c. phosphorus d. carbon
_____ 2. a. sp
What type of hybrid orbitals are used by the nitrogen atom in the molecule NH
3
? b. sp 2 c. sp 3 d. d 2 sp 3
_____ 3. What is the approximate H-N-H angle in NH
3
? a. 90 o
_____ 4. b. 108º c. 120 o d. 180 o
How many pi (π) bonds are found in the compound below?
CH
3
-CH=C-C≡ CH a. two b. three c. four d. five
(36)
_____ 5.
_____ 6.
Which of the following intermolecular forces is INCORRECTLY assigned as the principal force between units of the compound given? a.
CCl
4
, London b.
NH
3
, London c.
HF, H-bonding d.
CH
3
OH, H-bonding e.
H-Br, dipole-dipole
Which list of interparticle forces (between molecules of comparable size) is in order of increasing strength? (London = dispersion) a. London < ionic < H-bonds < dipole b. dipole < London < H-bond < ionic c. H-bond < ionic < dipole < London d. ionic < H-bond < London < dipole e. London < dipole < H-bond < ionic
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_____ 7. a. O
2
At STP which of the following species would have the highest average molecular speed? b. NO
2 c. N
2 d. HCl e. all would be the same
_____ 8 . The kinetic theory of gases does NOT include: a. The gas particles are very small and very far apart compared to their own sizes. b. The gas particles repel each other. c. The gas particles move randomly with a distribution of speeds. d. The gas particles collide with one another. e. The collisions between gas particles are elastic (no change in kinetic energy).
_____ 9. Arrange these substances in order of INCREASING boiling point: Xe, H
2
, H
2
O, LiCl,
H
2
S. a. Xe < H
2
< H
2
O < LiCl < H
2
S b. Xe < H
2
< H
2
S < H
2
O < LiCl c. H d. H
2
2
< Xe < H
< Xe < H
2
2
S < H
O < H
2
2
O < LiCl
S < LiCl
_____ 10. a. NH
3
Which of the following pure substances exhibits hydrogen bonding? b. H
2
S c. HCl d. CH
4 e. all of these do
_____ 11. Which of the following best describes the properties of a metallic solid? a.
soft, very low melting point, poor electrical conductor b. an amorphous solid with no unit cell, conducts electricity, doesn't conduct heat well c. very hard, very high melting point, poor electrical conductor d. variable hardness, variable melting point, excellent thermal conductor
_____ 12. An empirical equation which attempts to account for deviations of gases from ideal behavior is the van der Waal equation of state.
(P + n 2 a 2 /V 2 )(V - n b ) = nRT
In this equation, consider the following statements about the two parameters:
I. Parameter a accounts for weak attractive forces between the molecules.
II. Parameter b accounts for the physical sizes of the molecules themselves.
III. NH
3
would be expected to have a larger value of a than CH
4
. a. I is true, II is false, III is true b. I and II are true but III is false c. only III is true d. I, II, and III are true e. none are true
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_____ 13. The interaction responsible for the cohesive intermolecular forces of liquid nitrogen is: a. hydrogen bonding b. the London dispersion force c. dipole-dipole interaction d. covalent bonding
_____ 14. Identify the INCORRECT statement below: a. The vapor pressure of liquid water at 100°C is 760 torr (1 atm). b. The normal boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals 1 atm. c. The boiling point of a liquid increases as the surrounding pressure decreases. d. Vapor pressure of a liquid increases as the temperature increases. e. A liquid boils when its vapor pressure equals the surrounding pressure.
_____15. a. CH
4
Which of the following substances will have the highest boiling point? b. C
4
H
10 c. CH
3
CH
2
OH d. CH
3
OH
_____ 16. A fixed quantity of a gas is subjected to a decrease in pressure and an increase in temperature. The volume of the gas: a. remains the same b. decreases c. increases d. either increases or decreases, depending on the sizes of the pressure and temperature changes
_____ 17. Identify the INCORRECT statement below: a. The average speed of molecules of different gases depend on their molar mass. b. The average kinetic energy of gas molecules is directly proportional to the temperature of the sample. c. The average kinetic energies of molecules of different gaseous species are equal at a given temperature. d. All the molecules of a gaseous sample at a fixed temperature are traveling at the same speed at any given instance.
_____ 18. a. CH
4
Which of the following gases will have the fastest effusion rate? b. CO
2 c. N
2 d. O
2 e. Ar
3

II.
A 800.0 g sample of water is cooled from 150 o
C to solid at 0 o
C. sp.ht
steam
= 2.10 J/g o
C
 fus
= 0.332 kJ/g sp.ht
liq water
= 4.18 J/g o
C
 vap
= 2.26 kJ/g sp.ht
ice
= 2.09 J/g o
C a. Is the overall change endothermic or exothermic? Explain. b.
(2)
Explain what is happening on a molecular level at each step in the process.
Include types of motions. (6) c. Determine the total amount of energy exchanged by the system.
(Show all work)
(12)
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III.
Be sure to show all work for the problems below. a.
What is the pressure of 160.0 g of sulfur trioxide at 50 o C in a 200 L container? (9) b.
What is the molar mass of a gas if 14.0 g occupies 2.60 L at 40 o C and 1250 mmHg?
(10) c.
What is the temperature of a gas in o
C that occupies 380 mL at 900 mmHg if it has a volume of 410 mL at STP? (10)
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8. Answer any three of the following briefly but completely. You may answer a fourth for additional credit. (15) a. Why do you feel cold when you are wet and stand in windy conditions? b. Explain why alcohol or water will evaporate at room temperature (20 o
C) despite the fact that their boiling points are 80 and 100 degrees Celsius respectively. c. Autoclaves used to sterilize surgical equipment employ pure water that can boil at
150 o
C. Explain how this is possible. d. Systems always strive to achieve the lowest energy state. If this is the case, why does any liquid boil? e. You are doing an industrial reaction at 100 atm. You compress one reactant gas, expecting a volume of 550 L and find that the volume is actually 552 L. Explain this result.
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