NAME _____________________________________________ Student No. ______________
Section (circle one): A01 (Lipson)
A02 (Briggs)
A03 (Cartwright)
UNIVERSITY OF VICTORIA
Version
A
Version
A
CHEMISTRY 102
Mid-Term Test I – February 3,
2012
This test has two parts: (A Data Sheet is provided with the exam.)
PART I is a multiple choice examination and is worth 26 marks. The answers for the 14 questions in
this part must be coded on the optical sense form using a soft leaded pencil.
PART II has written answer questions and is on the last 3 pages and is worth 24 marks. Answer
these questions on this examination paper.
Part II
1 [8 marks]
2 [5 marks]
3 [4 marks]
4 [4 marks]
Score
Exam results
Score
Part I
[26 marks]
Part II
[24 marks]
Total score
[50 marks]
Percent score
5. [3 marks]
Hand in this entire test paper as well as your optical sense form at the end of the
examination period (60 minutes)
PART I – Multiple Choice. Select the best response from the choice provided. Mark only one response for
each question.
1.
This is exam version A. Mark "A" as the answer to question 1 on your bubble sheet.
2. To increase the volume of a fixed amount of gas from 200 mL to 400 mL
A. increase the temperature from 20.0 to 40.0 °C at constant pressure
B. increase the pressure from 2.00 to 4.00 atm at constant temperature
C. reduce the temperature from 527 °C to 127 °C at constant pressure
D. reduce the pressure from 0.80 atm to 304 mm Hg at constant temperature
E. increase the temperature from 400 K to 600 K.
Chem 102, Midterm 1
3.
Version A page 2 of 7
Of the following gases, which ONE has the greatest density at standard temperature and pressure?
A. CF4
B. NH3
D. H2
E. He
C. Ne
4. The addition of 2.0 g He(g) at 25 C to a fixed-volume container of 10.0 L that already contains H2(g) at a
temperature of 30 °C and a pressure of 0.980 atm will:
A. have no effect on the final gas pressure in the container
B. cause the final pressure in the container to exceed 4 atm
C. produce a 40% increase in gas pressure in the container
D. bring the final pressure in the container to just slightly less than 2.0 atm
E. cause the final pressure in the container to exceed 2 atm
5. If 1.0 L of CO2(g) is compared to 1.0 L of H2(g), when both samples at a temperature of 25 °C and one
atmosphere pressure, then:
A. the CO2 and H2 molecules have the same average speed
B. there are more H2 molecules than there are CO2 molecules
C. the average kinetic energy of the CO2 molecules is greater than that of the H2 molecules
D. the mass of the one liter sample of CO2 equals the mass of the one liter sample of H2
E. the H2 molecules are, on average, moving more quickly than the CO2 molecules
6. Which ONE of the following assumptions is NOT used to explain the ideal gas law?
A. gas particles themselves occupy a negligible percentage of the total gas volume
B. attractive and repulsive forces are negligible in gases
C. collisions between gas molecules are perfectly elastic
D. at constant temperature, all gas molecules have the same kinetic energy.
E. gas molecules are in continuous random motion
7.
The reason the stratosphere contains very little dissociated nitrogen (i.e. nitrogen atoms) is:
A. Nitrogen atoms are very reactive. They react with other substances immediately upon formation.
B. The dissociated nitrogen atoms very rapidly diffuse out of the atmosphere and into space.
C. The bond energy of nitrogen (N2) is very large and therefore N2 is difficult to photodissociate.
D. Most photodissociation of atmospheric N2 occurs in the troposphere and not the stratosphere.
E. There is no N2 in the stratosphere.
Chem 102, Midterm 1
Version A page 3 of 7
8. Which of the following molecules can be greenhouse gases?
(i) CO2
(ii) H2O
A. i, ii & vi
(iii) N2
(iv) Cl2
B. i & iv
(v) H2
(vi) NO2
C. i, ii & iii
D. i & v
E. i & vi
9. Which of the following statements about the atmosphere and atmospheric chemistry is INCORRECT?
A. Acidity caused by acid rain can be neutralized by adding limestone, CaCO3(s), to lakes.
B. The greenhouse effect contributes to maintaining a livable uniform temperature on the Earth’s
surface.
C. Photodissociation involves the removal of an electron from an atom or molecule as a result of
the absorption of a photon.
D. A key reaction in the production of smog is the photodissociation of NO2(g)
E. Acidified lakes have elevated concentrations of dissolved Al3+ ions, which are harmful to fish
populations.
10. Which of the following statements are CORRECT?
(i) SO2 is the only gas that contributes to the problem of acid rain.
(ii) N2, O2, and H2O are not greenhouse gases.
(iii) One human-caused imbalance is too little ozone in the stratosphere and too much in the
troposphere.
(iv) O3 in the atmosphere protects the earth from infrared radiation.
(v) The depletion of ozone over Antarctica is seasonal because it requires sunlight
A. i, iii, and v
B. ii, iii, and iv
C. ii, iii and v
D. ii and iii
E. iii and v
11. Which of the following is a CORRECT statement about a system and its surroundings during an energy
exchange?
A. The internal energy of the system is the sum of all the potential energies of its components.
B. A decrease in the volume of a system means that the internal energy of the system increases.
C. A system that releases heat to its surroundings gains internal energy.
D. If ΔEsystem < 0, the internal energy of both the system and the surroundings decreases.
E. The surroundings are the part of the universe that is studied.
Chem 102, Midterm 1
Version A page 4 of 7
12. If a reaction is carried out at constant pressure, which of the following statements is correct?
A. The reaction is likely to be exothermic.
cutoff for test #1.)
(This question dropped because it’s 10.3 and past the
B. The heat change is equal to the enthalpy change.
C. The reaction is likely to be endothermic
D. The heat change is smaller than the volume change.
E. The heat change is equal to the change in temperature.
13. Calculate the change in internal energy for the following situation: A balloon is cooled by removing
0.655 kJ of heat. The balloon shrinks, of course, and the atmosphere does 382 J of work on the
balloon.
ΔE for this process is…
A. -0.273 kJ
B. 273 J
D. 381 J
E. -381 J
C. 0.273 kJ
14. A gas is confined to a cylinder under a constant atmospheric pressure of 1 atm, as illustrated. The initial
volume is 3.0 L and the temperature is 300 K. The gas undergoes a chemical reaction; at the completion
of the reaction the final volume is 5.0 L and the final temperature is 310 K. Which of the following
statements correctly describes the changes in the system?
A. Work was done on the system and ΔH for the reaction is negative.
B. Work was done by the system and ΔH for the reaction is positive.
C. Work was done by the system and ΔH for the reaction is negative.
D. Work was done on the system and ΔH for the reaction is positive.
E. Work was done by the system and the sign of ΔH cannot be determined.
(This question dropped because it’s 10.3 and past the cutoff for test #1.)
Chem 102, Midterm 1
Version A page 5 of 7
Part II written answers to questions:
Write your answers directly on this test paper. Show all your work. Hand in the entire test
paper at the end of the test period.
8 marks
1. [3](a) A 0.500 m3 canister contains Freon-12 (CF2Cl2) at a pressure of 85.0 kPa at 23 °C. What mass of
Freon-12 does the canister contain (in kg)?
PV = nRT,
n = PV/RT = 85 kPa (103Pa/kPa) (0.5 m3) / [(8.314 m3Pa mol-1 K-1)(23 + 273)K] = 17.3 mol
grams of Freon-12 = (121 g mol-1) (17.3 mol) = 2090 grams = 2.09 kg
[2] b). Describe briefly, using a chemical equation, the useful function of the earth’s stratospheric ozone
layer.
The useful function of stratospheric ozone is that it protects plants and animals from
harmful ultra-violet radiation.
O3(g) + hv  O2(g) + O (g)
[3] c) Describe, using chemical equations, how chlorofluorocarbons like the Freon-12 in part (a) of this
problem, contribute to the depletion of the stratospheric ozone layer.
CF2Cl2(g) + hv  CF2Cl(g) + Cl(g)
Cl(g) + O3(g)  ClO(g) + O2(g)
with net result
2O3(g) (with Cl atoms as catalyst) 3O2(g)
(Photodissociation of freons releases chlorine atoms which then catalyze the destruction of ozone.)
Chem 102, Midterm 1
Version A page 6 of 7
5 marks
2.[3]a) An expandable container of volume 2.35 L is filled with O2(g) at 0 °C and a pressure of 1 atm. The
gas is allowed to expand to a volume of 5.00 L as a result of changes in pressure and temperature.
What is the density (in g/L) of the gas in the container under these changed conditions?
n(O2) = PV/RT = 1 atm x 2.35 L / [(0.08206 L atm mol-1 K-1)(273 K)] = 0.1049 mol
grams of O2 = 0.1049 mol x 32g / mol = 3.357 grams
density = 3.357 grams / 5.0 L = 0.671 g/L
(and of course it can be calculated using the SI units for R, as long as the appropriate unit conversions are
handled.)
[2] b). The container from part (a) above is again placed in the initial conditions at 0 °C and a pressure of 1
atm, producing a volume of 2.35 L What is the pressure (in atm) in the container if 0.30 mol of argon
[ Ar(g)] is added to the container and the temperature and volume are held constant?
mol (O2) [from (a)] = 0.1049 mol
total moles gas = 0.1049 + 0.30 = 0.4049 mol
P = ntotalRT/V = (0.4049 mol)( 0.08206 L atm mol-1 K-1)(273 K)/ 2.35 L = 3.86 atm = 3.9 atm
4 marks
3.
A gas is confined to a cylinder fitted with a piston and an electrical wire as shown below.
A current is supplied to the wire so that 137 J of energy is added to the system.
Consider two different cases: In Case #1 the piston is allowed to move as the energy is added.
In Case #2 the piston is fixed in place and cannot move.
Circle the correct response for each question below.
a)
In which case does the gas sample have the higher temperature after the addition
of the 137 J of electrical energy?
Case #1
b)
q
c)
Case #2
In Case #1, which quantity is larger (i.e. larger in magnitude)?
OR
w
OR
There’s not enough information to decide.
In Case #2, which quantity is larger (i.e. larger in magnitude)?
q
d)
or
OR
w
OR
There’s not enough information to decide.
The value of ΔE for the system (the confined gas) in the two cases is …
ΔE (Case #1) > ΔE (Case #2) OR ΔE (Case #1) < ΔE (Case #2) OR ΔE (Case #1) = ΔE (Case #2)
Chem 102, Midterm 1
Version A page 7 of 7
4 marks
4. [2](a) Is the measured pressure of a real gas lower or higher compared to that of an ideal gas? Explain
your answer.
At all pressures except extremely high ones, the measured pressure of a real gas is generally (i.e.
not so much for H2) lower than that expected for an ideal gas.
This is because there are intermolecular forces of attraction between real gas particles.
[2] b). Explain why a volume correction term is needed in the van der Waals equation for a real gas.
The particles that make up a gas actually take up space.
At very high pressures the space occupied by the real gas particles becomes a significant
fraction of the total gas volume and must be accounted for.
3 marks
5. Identify ONE reaction listed to the right that best matches each chemical processes listed on the left.
a) Neutralization of acid rain by
limestone____D______
A. 2 NO(g) + O2(g)
B. CaCO3(s)
b) Reaction used to remove the sulfur
produced by burning fossil fuels
_H (or B)_(but only one of these is
expected as answer)___
c) Reaction that contributes to
photochemical smog___A__
d) Reaction involved in the
degradation of statues and
buildings__D__
e) Formation of one component of
acid rain___C_____
2 NO2(g)
CaO(s) + CO2(g)
C. SO3(g) + H2O(ℓ)
H2SO4(aq)
D. CaCO3(s) + 2 H+(aq)
E. CO2(g) + H2O(ℓ)
Ca2+(aq) + CO2(g) + H2O(aq)
H2CO3(aq)
F. ClOOCl(g) + uv light
G. 6 CO2(g) + 6 H2O(ℓ)
H. CaO(s) + SO2(g)
I. C6H12O6(aq)
yeast
2 Cl(g) + O2(g)
plants
C6H12O6(aq) + 6 O2(g)
CaSO3(s)
2 C2H5OH(aq) + 2 CO2(g)
f) Dissolution of carbon dioxide in the
ocean___E___
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