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551-534
Chemistry
Comprehensive Exam
Number 55
GUIDE
Secondary 5
September, 2005
Guide
1.
Page 1
GENERAL INFORMATION
1.1
Program:
Chemistry, Secondary V
1.2
Origin:
Mathematics and Science & Technology Committee, 2005
Computerization and graphics: Martine Sanscartier
Revision: Patricia Juliano, BIM, Société GRICS
1.3
Time allotted: 2 hours 30 minutes
1.4
Number of questions: 29 distributed as follows: 14 multiple choice
15 constructed response (students select 11)
Structure of the Exam:
551-534.E55
Part A:
Fourteen (14) multiple-choice questions worth 4 marks each for a total
of 56%.
Part B:
Four (4) problems on the gases and their applications of which the
student is required to answer three (3). Each question is worth 4 marks
for a total of 12%.
Part C:
Four (4) problems on energy in chemical reactions of which the
student is required to answer three (3). Each question is worth 4 marks
for a total of 12%.
Part D :
Three (3) problems on rate of chemical reactions (kinetics) of which
the student is required to answer two (2). Each question is worth 4
marks for a total of 8%.
Part E :
Four (4) problems on chemical equilibrium of which the student is
required to answer three (3). Each question is worth 4 marks for a total
of 12%.
Guide
1.5
2.
Page 2
Authorized material: - drawing instruments, graph paper
- scientific calculator with or without graphic display
- list of formulas and quantities included in the
examination booklet
- periodic table of the elements included in the
examination booklet
- a table of reduction potentials included in the
examination booklet
DESCRIPTION OF EXAM
The following table matches each of the examination questions with the corresponding
dimension of the definition of the domain that was used for the examination.
Exam Specifications
Topics
Gases and their
Applications
28%
Energy in
Chemical
Reactions
28%
Rate of
Chemical
Reactions
16%
Equilibrium in
Chemical
Reactions
28%
Mastery of
Concepts
28%
2, 4
5, 8
9, 10
13
Mastery of
Applications
28% – 40%*
1, 3
6, 22
23, 24
11, 12, 14, 28
Mastery of
Problem- Solving
Techniques
32% – 44%*
15, 16, 17, 18
7, 19, 20, 21
25
26, 27, 29
Skill
The numbers on the centre of each box above represent the question numbers in the examination.
*Depending on questions chosen.
The examination consists of the following types of questions:
14 multiple-choice questions (numbers 1 - 14) that test the student's mastery of concepts and
applications.
11 of 15 constructed-response questions (numbers 15 - 29) that test the student's mastery of concepts,
applications and problem solving.
Student selection of problems
When a student answers more than the number of questions required, without indicating which ones are to
be corrected, only the first ones are to be corrected. Thus, for example, if a student is to choose two out
of three questions and answers all three, only the first two are to be corrected.
551-534.E55
Guide
Page 3
ITEM SPECIFICATIONS
Question
MOD.TO.IO
T
S
D
Part A
1
2
3
4
5
6
7
8
9
10
11
12
13
14
[2153]
[2154]
[2155]
[2156]
[2157]
[2158]
[2159]
[2160]
[2161]
[2162]
[2163]
[2164]
[2165]
[2166]
M02.01.01
M02.02.02
M02.02.04
M02.02.09
M03.03.02
M03.01.01
M03.02.04
M03.02.05
M04.02.01
M04.02
M05.01
M05.01.03
M05.02.02
M05.03
M
M
M
M
M
M
M
M
M
M
M
M
M
M
C
C
C
C
C
C
A
A
C
C
C
A
A
A
E
M
E
E
M
E
M
D
E
E
E
M
E
E
Part B
15
16
17
18
[2167]
[2168]
[2169]
[2170]
M02.02.02
M02.02.09
M02.02.07
M02.03.02
E
E
E
E
A
P
P
C
D
M
M
E
Part C
19
20
21
22
[2171]
[2172]
[2173]
[2174]
M03.02.06
M03.02.03
M03.03
M03.03.03
E
E
E
E
P
A
A
A
M
M
M
D
Part D
23
[2175] M04.01.02
24
[2176] M04.02.02
25
[2177] M04.03
E
E
E
A
C
A
M
M
M
Part E
26
27
28
29
E
E
E
E
P
P
P
P
M
D
M
M
[2178]
[2179]
[2180]
[2181]
551-534.E55
M05.02.06
M05.02.05
M05.03.04
M05.03.05
Legend:
MOD : Modules
M02: Gases and Their Applications
M03: Energy in Chemical Reactions
M04: Rate of Chemical Reactions
M05: Equilibrium in Chemical Reaction
TO:
Terminal objective
IO:
Intermediate objective
T:
Type
M : multiple-choice
E : extended-answer (constructed response)
S:
Skill
C : Mastery of Concepts
A : Mastery of Application
P : Mastery of Problem-Solving Techniques
D:
Level of difficulty
E:
Easy
M:
Medium
D:
Difficult
Guide
3.
CORRECTION KEY
Part A
4 marks or 0 marks
1
D
2
D
3
C
4
A
5
C
6
D
7
C
8
A
9
A
10
D
11
B
12
C
13
C
14
B
551-534.E55
Page 4
Guide
Page 5
GUIDELINES FOR CORRECTING CONSTRUCTED-RESPONSE QUESTIONS
Below is an explanation of the terms found in the marking scale to be used for scoring the
answers to the constructed response questions in the examination.
It is IMPORTANT that the teacher read this information carefully before correcting the
examination.
Constructed-response questions usually consist of two parts: the procedure used to solve the
problem and the answer. Thus, a constructed-response question should be corrected in two steps.
Step 1
Analyze the work to understand the procedure used by the student, and then decide if the
procedure is appropriate or not.
A procedure is appropriate if the steps presented could lead to the correct answer.
A procedure is partially appropriate if the steps presented do not lead to the correct answer,
but include at least one step that is relevant and correct.
A procedure is inappropriate if none of the steps presented are relevant or if the student has
not shown any work.
Step 2
If the procedure is deemed appropriate, then evaluate the answer. If the answer is incorrect,
identify the type of error made.
The error is considered minor if it is an error in calculation or transcription, if the unit of
measurement is incorrect or missing, or if the student has rounded off a number incorrectly.
The error is considered major if a law, rule, or formula has been applied incorrectly.
No marks are allotted for a correct answer when the procedure used is inappropriate.
551-534.E55
Guide
Page 6
Part B
15
Example of an appropriate and complete solution
P1V1
n1T1
=
P2V2
n2T2
P1 (2 L)
n (293 K)
=
P2 (0.5 L)
0.5 n (253 K)
P1 (2 L)
n (293 K)
=
P2 (0.5 L)
0.5 n (253 K)
2L
253 K (0.5 n)

P1
=
n (293 K)
(0.5 L)
1.73 P1
P2
=
P2
Answer: The ratio is 1.73 : 1.
4 marks
Appropriate and complete procedure.
3 marks
Appropriate procedure with a minor error such as calculation or transcription error.
2 marks
Appropriate procedure with a major error such as the incorrect application of a law,
formula or rule.
1 mark
Partially appropriate and correctly completed procedure.
0 marks
Inappropriate procedure or did not show the procedure, regardless of the answer.
551-534.E55
Guide
16
Page 7
Example of an appropriate and complete solution
Step 1:
Find mass of nitroglycerine.
1.59 g
d=
mL
mass
1.59 g
=
mL
100 mL
159 g of nitroglycerine present in 100 mL.
Step 2:
Find moles of H2O gas
M for nitro glycerine =
227 g
mol
159 g
= 0.70 mol of nitro glycerine
227 g
mol
4 mol C3H5 ONO2 3(l)
0.70 mol C3H5 ONO2 3(l)
=
10 mol H 2 O (g)
x mol H 2 O (g)
x = 1.75 mol H2O(g)
Step 3:
Find volume H20(g)
Use either:
A. Ideal gas Law, PV= nRT
or
B. Avogadro, at STP 1 mol gas = 22.4 L
Answer: The volume of water vapour produced is 39 L.
4 marks
Appropriate and complete procedure.
3 marks
Appropriate procedure with a minor error such as calculation or transcription error.
2 marks
Appropriate procedure with a major error such as the incorrect application of a law,
formula or rule. (i.e. Student did not convert to mass.)
1 mark
Partially appropriate and correctly completed procedure.
0 marks
Inappropriate procedure or did not show the procedure, regardless of the answer.
551-534.E55
Guide
17
Page 8
Example of an appropriate and complete solution
Mass of unknown gas
47.61 g  46.02 g = 0.69 g
PV
=
n
=
=
=
nRT
PV
RT
46.9 kPa  0.296 L
kPa L
8.31
 18  273
mol K
0.00574 mols unknown gas
Molar mass of unknown gas
0.69 g
0.00574 mols
= 120.2 g/mol
Therefore, the unknown gas is CF2Cl2
Answer: The unknown gas is most likely CF2Cl2 because its molar mass is 121 g/mol.
4 marks
Appropriate and correct answer.
3 marks
Appropriate procedure with a minor error such as calculation or transcription error.
2 marks
Appropriate procedure with a major error such as the incorrect application of a law,
formula or rule.
1 mark
Partially appropriate and correctly completed procedure.
0 marks
Inappropriate procedure or did not show the procedure, regardless of the answer.
551-534.E55
Guide
18
Page 9
Example of an appropriate and complete solution
a)
Temperature has a direct effect on the average kinetic energy of a molecule. Colder
temperatures imply that the molecules will move at a slower rate. Since the molecules
are moving at a slower rate they will diffuse (spread out) at a slower pace.
b)
The molecular mass of helium is less than the molar mass of oxygen. Because both gases
have the same kinetic energy, the velocity of the helium molecules must be greater than
the velocity of the helium molecules must be greater than the velocity of the oxygen
molecules. Therefore helium will diffuse more rapidly.
a)
1 mark for temperature affecting energy
1 mark for energy resulting in slower rate
b)
1 mark for comparing the molar mass of the two gases
1 mark for correctly relating mass, velocity, and rate of diffusion
551-534.E55
Guide
Page 10
Part C
19
Example of an appropriate and complete solution
Twater =
26 °C  14 °C = 12 °C
Tx =
95 °C  26 °C = 69 °C
MwCw Tw = MxCx Tx
M C ΔTw
Cx
= w w
M x ΔTx
65 g 12 C 4.19 J/g C
=
150 g  69 C
= 0.32 J/g °C
Answer:
The specific heat capacity of the unknown metal is 0.32 J/g °C.
4 marks
Appropriate and complete procedure.
3 marks
Appropriate procedure with a minor error such as calculation or transcription error.
2 marks
Appropriate procedure with a major error such as the incorrect application of a law,
formula or rule. (i.e. Students reversed the T’s or reversed the constants.)
1 mark
Partially appropriate and correctly completed procedure.
0 marks
Inappropriate procedure or did not show the procedure, regardless of the answer.
551-534.E55
Guide
20
Page 11
Example of an appropriate and complete solution
1.
Moles of NaOH(aq) used
n
or n = MV
V
(1.0 mol/L)(50.0 mL/1000mL) = 0.050 moles
M=
2.
Heat absorbed
Q = mcT
(70.0 g)(4.19 J/(goC)(29.8-22.3 °C) = 2200 J
3.
Since Q for the surroundings is positive, Q for the system must be negative (or -2200 J)
4.
Molar heat of neutralization
Q
H =
n
- 2200 J
NaOH
0.050 moles
-44000 J or -44 kJ/mol NaOH
Answer:
H is -44 kJ/mol NaOH.
4 marks
Appropriate and complete procedure.
3 marks
Appropriate procedure with a minor error such as calculation or transcription error, or
units of measurement missing.
2 marks
Appropriate procedure with a major error such as the incorrect application of a law,
formula or rule.
1 mark
Partially appropriate and correctly completed procedure.
0 marks
Inappropriate procedure or did not show the procedure, regardless of the answer.
551-534.E55
Guide
21
Page 12
Example of an appropriate and complete solution
Moles of diamond used
1.00 g
= 8.33  10-2 mol C
12.01 g/mol
Q = mcwater T
= (150.0 g)(4.19 J/(g°C)(74.5 – 22.0 °C)
= 3.30  104 J
Q for diamonds is -3.30  104 J or -3.30  101 kJ
Molar Heat of Combustion
Q
- 3.30  101 kJ
=
n
8.33  10  2 moles

=
Answer:



-396 kJ/mol
H is -396 kJ/mol or -396 000 J/mol.
4 marks
Appropriate and complete procedure.
3 marks
Appropriate procedure with a minor error such as calculation or transcription error or
omission of the negative sign.
2 marks
Appropriate procedure with a major error such as the incorrect application of a law,
formula or rule.
1 mark
Partially appropriate and correctly completed procedure.
0 marks
Inappropriate procedure or did not show the procedure, regardless of the answer.
551-534.E55
Guide
22
Page 13
Examples of an appropriate and complete solution
N+3H
1118 kJ -
Enthalpy or Ep
(kJ/mol)
0.0 -
1
2
3
N2 + 2 H2
H
NH3
-46 -
Reaction coordinate
Criteria:
1.
y axis is labelled correctly, including units and values.
2.
Correct H.
3.
Activation energy values are correctly indicated.
4.
Reactants, activated complex, and products are correctly labelled.
Allot 1 mark per criterion.
Note:
551-534.E55
Students may use arrows to indicate the difference in energy levels rather than
indicating numbers on the y axis.
Guide
Page 14
Part D
23
Example of an appropriate and complete answer
Rate of N2 consumption
0.60  4.00 mol/L = -0.068 or -6.8  102 mol/L/min
50 min
Rate of NH3 production
2 mol NH3
- 6.8  10-2 mo l/L

= 1.4  101 mol/L/min
1 mol N 2
min
Answer:
24
The average rate of ammonia production is 1.4  101 mol/L/min.
4 marks
Appropriate and complete procedure.
3 marks
Appropriate procedure with a minor error such as calculation or transcription error or
an incorrect or missing unit of measurement in the answer.
2 marks
Appropriate procedure with a major error such as the incorrect application of a law,
formula or rule.
1 mark
Partially appropriate and correctly completed procedure.
0 marks
Inappropriate procedure or did not show the procedure, regardless of the answer.
Example of an appropriate and complete solution
(I)
(II)
(III)
NO
OH
OH and NO
Allot 1 mark for each correct substance listed.
Deduct 1 mark for each incorrect substance listed.
551-534.E55
Guide
25
Page 15
Example of an appropriate and complete solution
a)
Data Table
Time (min)
0.0
0.2
0.4
0.6
0.8
1.0
[I-] (mol/L)
0.0800
0.0400
0.0200
0.0100
0.0050
0.0025
[I2] (mol/L)
0
0.02
0.03
0.035
0.0375
0.0387
3 marks
Deduct 1 mark per error
b)
Calculate the rate
Rate
=
0.03875  0 mol/L
1.0  0.0 min
0.03875 mol/L
=
1.0 min
= 0.03875 mol/L/min
= 3.88  10-2
= 3.9  10-2 mol/L/min
Answer: The average rate of reaction for the production of I2(aq) is 3.9  10-2 mol/L/min.
1 mark
551-534.E55
Guide
Page 16
Part E
26
Example of an appropriate and complete answer
I
C
E
Kc

4 NH3(g)
+ 3 O2(g)
0.0150
0.0150
-3.92  103
-2.94  103
1.11  102
1.21  102
=
2 N2(g)
+ 6 H2O(g)
0
0
+1.96  103
+5.88  103
+1.96  103
+5.88  103
N 2  2 H 2O 6
NH3  4 O2  3
1.96  10
=
1.11  10
3
2
 5.88  10
mol/L  1.21  10
2
mol/L
4
3
3
2

mol/L 
mol/L
6
3
= 6.01  106
Answer: The Kc for the reaction at this temperature is 6.01  106.
4 marks
Appropriate and complete procedure.
3 marks
Appropriate procedure with a minor error such as calculation or transcription error.
2 marks
Appropriate procedure with a major error such as the incorrect application of a law,
formula or rule.
1 mark
Partially appropriate and correctly completed procedure.
0 marks
Inappropriate procedure or did not show the procedure, regardless of the answer.
551-534.E55
Guide
27
Page 17
Example of an appropriate and complete solution
Butanoic Acid
HA
0.15
-1.51  103
0.148
I
C
E
Ka
1.51  10

3
mol/L
0.148 mol/L
1.54  105
=
=

H+
0
1.51  103
1.51  103
+ A
H+
0
1.32  105
1.32  105
+ A
0
+ 1.51  103
1.51  103
2
Hydrofluoric Acid
First find H+
KW
= 1.32  105
7.59  10 10
HA
0.035
-1.32  105
0.035
I
C
E
Ka
=
=
Answer:
1.32  10
5

mol/L
0.0350 mol/L
4.98  109

0
+ 1.32  105
1.32  105
2
Butanoic acid is the stronger of the two.
Note:
Comparing percent ionization is an acceptable justification.
4 marks
Appropriate procedure and correct answer.
3 marks
Appropriate procedure with a minor error such as calculation or transcription error.
2 marks
Appropriate procedure with a major error such as the incorrect application of a law,
formula or rule.
1 mark
Partially appropriate and correctly completed procedure.
0 marks
Inappropriate procedure or did not show the procedure, regardless of the answer.
551-534.E55
Guide
28
Page 18
Example of an appropriate and complete answer
a)
e
Anode, Mg
V
Cathode, Ag
salt bridge
Mg2+
Mg(s)  Mg2+(aq) + 2e
E° = 2.37 V
Ag+
Ag+(aq) + e  Ag(s)
E° = 0.80 V
b)
E°cell : 2.37 V + 0.80 V = 3.17 V
c)
To increase the cell potential, the concentration of AgNO3 should be increased or the
concentration of Mg(NO3)2 should be decreased.
4 marks
Appropriate and complete procedure.
3 marks
Appropriate procedure with a minor error such as calculation or transcription error.
2 marks
Appropriate procedure with a major error such as the incorrect application of a law,
formula or rule.
1 mark
Partially appropriate and correctly completed procedure.
0 marks
Inappropriate procedure or did not show the procedure.
551-534.E55
Guide
29
Page 19
Example of an appropriate and complete answer
1.
2.
3.
Fe2+ + 2e  Fe
Cu  Cu2+ + 2e
 0.44 V
 0.34 V
 0.78 V
Maintains integrity of pipes
(1 mark)
Pb2+ + 2e  Pb
Cu  Cu2+ + 2e
 0.13 V
 0.34 V
 0.47 V
Maintains integrity of pipes
(1 mark)
2 Ag+ + 2e  2 Ag
Cu  Cu2+ + 2e
+ 0.80 V
 0.34 V
+ 0.46 V
Answer:
551-534.E55
Copper pipe corrodes
(1 mark)
The technician did cause chemical reaction to occur in the pipes because silver
nitrate corrodes copper pipes.
(1 mark)
551-534
Chemistry
Comprehensive Exam
Number 55
Question Booklet
Secondary 5
September, 2005
Question Booklet
Page 1
INSTRUCTIONS
1.
Write the required information on the title page of the Answer Booklet.
2.
Answer all questions in the Answer Booklet. Each question is worth four marks.
3.
In Part B, you are to answer 3 of the 4 questions.
4.
In Part C, you are to answer 3 of the 4 questions.
5.
In Part D, you are to answer 2 of the 3 questions.
6.
In Part E, you are to answer 3 of the 4 questions.
7.
You may use drawing instruments, graph paper and a scientific calculator with or without
graphing display.
8.
You may refer to the lists of formulas, quantities, and tables included in this Question
Booklet. The use of any other source of reference is strictly forbidden.
9.
Hand in both the Question Booklet and the Answer Booklet at the end of the exam
session.
Note: Figures are NOT necessarily drawn to scale.
Time allotted: 2 hours 30 minutes
551-534.E55
Question Booklet
551-534.E55
Page 2
Question Booklet
Page 3
FORMULAS
Q = mcT
PV = n RT
P1V1 P2V2
=
n1T1 n2T2
PHYSICAL CONSTANTS
SYMBOL
c H 2O
VALUE
NAME
Specific heat capacity of
water
4190 J/(kg°C)
or
 H 2O
R
551-534.E55
Density of water
Molar gas constant
4.19 J/(g°C)
1.00 g/mL
8.31 kPa  L/(molK)
Question Booklet
Page 4
Standard Reduction Potentials
ION CONCENTRATION of 1 mol/L at 25°C and 101.3 kPa.
Reduction Half-reaction
F2(g)
Au3+(aq)
Cl2(g)
Br2(aq)
Br2(l)
Ag+(aq)
Hg 2+(aq)
Fe3+(aq)
I2(s)
Cu+(aq)
Cu2+(aq)
2H+(aq)
Pb2+(aq)
Sn2+(aq)
Ni2+(aq)
Co2+(aq)
Fe2+(aq)
Cr3+(aq)
Zn2+(aq)
Cr2+(aq)
Mn2+(aq)
Al3+(aq)
Be2+(aq)
Mg2+(aq)
Na+(aq)
Ca2+(aq)
Sr2+(aq)
Ba2+(aq)
Cs+(aq)
K+(aq)
Rb+(aq)
Li+(aq)
551-534.E55
+ 2e+ 3e+ 2e+ 2e+ 2e+ e+ 2e+ e+ 2e+ e+ 2e+ 2e+ 2e+ 2e+ 2e+ 2e+ 2e+ 3e+ 2e+ 2e+ 2e+ 3e+ 2e+ 2e+ e+ 2e+ 2e+ 2e+ e+ e+ e+ e-
































2F-(aq)
Au(s)
2Cl-(aq)
2Br-(aq)
2Br-(aq)
Ag(s)
Hg(l)
Fe2+(aq)
2I-(aq)
Cu(s)
Cu(s)
H2(g)
Pb(s)
Sn(s)
Ni(s)
Co(s)
Fe(s)
Cr(s)
Zn(s)
Cr(s)
Mn(s)
Al(s)
Be(s)
Mg(s)
Na(s)
Ca(s)
Sr(s)
Ba(s)
Cs(s)
K(s)
Rb(s)
Li(s)
Reduction Potential (V)
E° = + 2.87
E° = + 1.50
E° = + 1.36
E° =+ 1.09
E° =+ 1.07
E° = + 0.80
E° = + 0.78
E° = + 0.77
E° = + 0.53
E° = + 0.52
E° = + 0.34
E° = + 0.00
E° = - 0.13
E° = - 0.14
E° = - 0.26
E° = - 0.28
E° = - 0.44
E° = - 0.74
E° = - 0.76
E° = - 0.91
E° = - 1.18
E° = - 1.66
E° = - 1.85
E° = - 2.37
E° = - 2.71
E° = - 2.87
E° = - 2.89
E° = - 2.91
E° = - 2.92
E° = - 2.93
E° = - 2.98
E° = - 3.04
Question Booklet
Page 5
Part A
Questions 1 to 14
Blacken the letter that corresponds to your answer in the answer booklet.
1
2
Which of the following statement is TRUE?
A)
Gas molecules are strongly attracted to each other.
B)
At a given temperature, the number of degrees Celsius is always larger than the
number of Kelvins.
C)
For a fixed amount of gas at a constant pressure, if temperature increases, volume
decreases.
D)
For a fixed amount of gas at a constant volume, if temperature increases, pressure
increases.
The Kinetic Molecular Theory describes an ideal gas model. Among the main features of this
model are:
(I)
(II)
(III)
(IV)
Gases consist of molecular particles moving at any given instant in straight lines.
Molecules collide with each other and with the container walls without loss of
kinetic energy.
The average kinetic energy of gas molecules is directly proportional to the Kelvin
temperature.
Gas molecules are very widely spaced, relative to the size of the molecules.
Which two of these Kinetic Molecular Theory features can be used to explain why gas
bubbles always rise through a liquid and become larger as they move upward?
3
A)
(I) and (III)
C)
(II) and (III)
B)
(I) and (IV)
D)
(II) and (IV)
There are n molecules in 250 cm3 of hydrogen gas (H2), at a certain temperature and pressure.
How many molecules are in 1.0 L of oxygen gas (O2) under the same conditions of
temperature and pressure?
A)
n
C)
4n
B)
2n
D)
8n
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Question Booklet
4
Page 6
Consider the following two situations concerning gases.
(I)
Included on all spray cans is a warning to not incinerate the can even if it is empty, and to
always store it below 40°C.
(II)
When you examine the tires on your bicycle before you start out in the morning, you note
that they appear slightly soft. However, after riding for several hours, they get harder.
Which of the following graphs can be used to explain these two situations?
A)
C)
P
P
T
B)
D)
V
T
551-534.E55
V
n
T
Question Booklet
5
Page 7
The enthalpy diagram below shows the energy involved in the formation of CO2(g).
Energy (kJ/mol)
C(s) + O2(g)  CO2(g)
Time
Once the reaction above has been initiated, which of the following statements is true?
6
A)
The formation of CO2(g) constitutes an endothermic reaction.
B)
The formation of CO2(g) does not result in energy from the system being transferred
into the surroundings.
C)
The formation of CO2(g) results in energy from the system being transferred into the
surroundings.
D)
In the formation of CO2(g) the enthalpy of the products will be greater than the
enthalpy of the reactants.
Everyday, phenomena take place all around us.
Which of the following may be identified as exothermic processes?
1.
2.
3.
4.
5.
Dew forming on blades of grass
Melting snow and ice on a driveway by adding salt
Drying a wet T-shirt on a clothesline
Freezing meat to preserve it
Burning propane gas in a stove
A)
2 and 3
C)
1, 2 and 3
B)
4 and 5
D)
1, 4 and 5
551-534.E55
Question Booklet
7
Page 8
Ethane, C2H6, can be decomposed into ethene, C2H4, and hydrogen gas:
C2H6(g)  C2H4(g) + H2(g)
Using the following equations, determine the enthalpy change for the decomposition of
ethane.
2 H2(g) + O2(g)  2 H2O(l)
C2H4(g) + 3 O2(g)  2 H2O(l) + 2 CO2(g)
2 C2H6(g) + 7 O2(g)  6 H2O(l) + 4 CO2(g)
1.
2.
3.
8
H = -572 kJ
H = -1401 kJ
H = -3100 kJ
A)
-5073 kJ
C)
137 kJ
B)
-3237 kJ
D)
3237 kJ
Barbeque propane gas, C3H8, burns according to the following equation:
C3H8 (g) + 5 O2 (g)  3 CO2 (g) + 4 H2O (g)
How many grams of propane are needed to provide the 980 kJ required to cook a salmon
steak?
∆Hf (kJ/mol)
3 C(s) + 4 H2(g)  C3H8(g)
-103.8
C(s) + O2(g)  CO2(g)
-394.0
H2(g) + ½ O2(g)  H2O(g)
-241.8
A)
21.1 g
C)
9.6 g
B)
19.1 g
D)
10.6 g
551-534.E55
Question Booklet
9
10
Page 9
Which of the following does not affect the reaction rate?
A)
Nature of products
B)
Surface area of reactants
C)
Concentration of reactants
D)
Presence of a catalyst
Consider the following reactions at room temperature:
1.
Fe3+(aq) + SCN1-(aq)  FeSCN2+ (aq)
2.
4 Fe(s) + 3 O2(g)  2 Fe2O3(s)
3.
8 Fe(s) + S8(s)  8 FeS(s)
Which combination below arranges the reactions from slowest to fastest?
11
A)
1  2  3
C)
2  3  1
B)
1  3  2
D)
3  2  1
The equilibrium constant (Kc) for the following reaction is 1.47  103.
H3O+(aq) + F-(aq)  HF(aq) + H2O(l)
At equilibrium, which of the following statements about the reaction is true?
A)
The concentration of H3O+ and F- would be much larger than HF.
B)
The concentration of HF would be much larger than H3O+ and F-.
C)
The concentration of H3O+ , F- and HF would be approximately equal.
D)
Kc has no effect on concentration.
551-534.E55
Question Booklet
12
Page 10
Consider the following reaction at equilibrium in a closed container:
CaCO3(s)  CaO(s) + CO2(g)
Which of the following statements is true if the volume of the container is increased?
13
A)
The concentration of CaCO3 would increase.
B)
The concentration of CaCO3 would decrease.
C)
The amount of CO2 would increase.
D)
The amount of CO2 would decrease.
Propanoic acid (CH3CH2COOH which we simplify as HPr) is an organic acid whose salts are
used to retard mould growth in foods.
The balanced equation is shown below:
HPr(aq) + H2O(l)  Pr-(aq) + H3O+(aq)
Which of the following is the correct expression for the acid dissociation constant?
A)
B)
14
 

C)
Pr H O 
D)
K a  Pr  H 3O 
Ka 


3
HPr H 2O
Ka 
Ka 
Pr H O 

HPr 
HPr H 2O
Pr H O 


3
Consider the following redox reaction:
Sr(s) + Mg2+(aq)  Sr2+(aq) + Mg(s)
Which is the oxidizing agent?
A)
Sr
C)
Sr2+
B)
Mg2+
D)
Mg
551-534.E55

3
Question Booklet
Page 11
Parts B, C, D and E of the examination comprise questions for which you must show all your work.
Answer these questions in the answer booklet. Show all the work needed to solve the problem: data
given, explanations, formulas and calculations. Then write your answer in the space provided. You
will be given no marks if you provide the right answer without showing your work. However, you will
be given part marks for work that is partially correct. Where necessary, the correct unit of
measurement must be included in the answer; however, significant figures will not be considered.
Part B
Questions 15, 16, 17 and 18 (Answer three questions only.)
If you answer all questions in this section, draw a line through the question that you
do not want to have corrected. If you do not, questions 15, 16 and 17 will be corrected.
15
A student produced H2(g) by performing the following chemical reaction:
Mg(s) + 2 HCl(aq)  MgCl2(aq) + H2(g)
The hydrogen gas produced was collected and stored in a 2.00 L container at 20.0 °C.
Half of the original amount of the gas is transferred into a 0.50 L container at -20.0 °C.
What is the ratio of the gas pressure in the second container to the initial gas pressure in
the first container?
Show all your calculations to justify your answer.
16
Nitroglycerine, C3H5(ONO2)3, has a density of 1.59 g/mL. When it explodes, the following
reaction takes place:
4 C3H5(ONO2)3 (l)  12 CO2(g) + O2(g) + 6 N2(g) + 10 H2O(g)
What volume of water vapour, measured at STP, is produced when 1.0 x 102 mL of
nitroglycerine explodes?
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Question Booklet
17
Page 12
The product formed in a controlled fluorination of CHCl3 is a gaseous compound. To identify it,
a flask is evacuated and the unknown gas is transferred into the flask. The data below is
collected:
Volume of evacuated flask
296.0 mL
Mass of evacuated flask
46.02 g
Mass of flask + unknown gas
46.71 g
Pressure
46.9 kPa
Temperature
18.0 °C
Which of the following is most likely the unknown gas?
CFCl3
CF2Cl2 CF3Cl CF4
Show all your calculations and justify your choice.
18
Using the Kinetic Molecular Theory of gases explain why:
a)
The rate of diffusion of a gas decreases when the temperature is reduced.
b)
Under the same conditions, the rate of diffusion of helium gas is greater than the rate of
diffusion of oxygen gas.
551-534.E55
Question Booklet
Page 13
Part C
Questions 19, 20, 21 and 22 (Answer three questions only.)
If you answer all questions in this section, draw a line through the question that you
do not want to have corrected. If you do not, questions 19, 20 and 21 will be corrected.
19
An unknown metal with a mass of 150 g and a temperature of 95 °C is placed into a Styrofoam
cup containing 65 g of water at a temperature of 14 °C. When the system reaches equilibrium,
the resulting temperature is 26 °C.
What is the specific heat capacity of the unknown metal? (Assume no loss of heat energy to
the surroundings.)
20
A calorimeter is filled with 50.0 mL of 1.0 mol/L NaOH(aq) at an initial temperature of 22.3 °C
and 20.0 mL of 2.5 mol/L HCl(aq) is added at this same temperature. After the neutralization
reaction comes to completion, the final temperature of the resulting solution is found to be
29.8 °C.
Determine the H (kJ/mol) for the neutralization for the reaction with respect to the
NaOH(aq) solution. (Assume the density and specific heat for all solutions to be equal to that of
water)
551-534.E55
Question Booklet
21
Page 14
A bomb calorimeter contains a 150.0 g of water at an initial temperature of 22.0 °C. When 1.00 g
of diamond is burned in the calorimeter to produce CO2, the final temperature of the water
reaches 74.5 °C.
What is the H (kJ/mol) for the combustion of carbon in the form of diamond?
C(diamond) + O2(g) 
22
H = ?
CO2(g)
The Haber process for the formation of ammonia (NH3)) from the elements can be derived from
the following equations:
1
2
N2(g) +
3
2
H2(g) 
N(g) + 3 H(g) Eactivation = 1118 kJ
NH3(g) 
N(g) + 3 H(g) Eactivation = 1164 kJ
The Haber process can be written as
1
2
N2(g) +
3
2
H2(g)

NH3(g)
N(g) + 3 H(g) has been determined to be the activated complex for the overall reaction.
Draw an Enthalpy diagram to determine the H for the Haber process. Indicate the H on
the diagram. The graph must indicate reactants, products, activated complex, H, and
appropriate values.
551-534.E55
Question Booklet
Page 15
Part D
Questions 23, 24 and 25 (Answer two questions only.)
If you answer all questions in this section, draw a line through the question that you
do not want to have corrected. If you do not, questions 23 and 24 will be corrected.
Consider the following graph, illustrating nitrogen consumption.
Consumption of Nitrogen
Concentration (mol/L) of Nitrogen
23
4.50
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
0
10
20
30
40
50
60
70
Time (min)
In the Haber reaction, nitrogen gas (N2) is combined with hydrogen gas (H2) under extremely
high pressure and medium temperature, and using a catalyst (an iron catalyst prepared by
reducing magnetite, Fe3O4), to produce ammonia (NH3(g)).
N2(g) + 3 H2(g) 
2 NH3(g)
Using the graph above, calculate the average rate of ammonia production in mol/L/min
over the first fifty (50) minutes.
551-534.E55
Question Booklet
24
Page 16
Shown below are several reaction mechanisms involving Ozone gas (O3).
(I) NO(g) + O3(g)
O(g) + NO2(g)


NO2(g) + O(g)
NO(g) + O2(g)
(II) OHHO2


HO2 + O2(g)
OH- + 2O2(g)





H(g) + CO2(g)
HO2
OH- + NO2(g)
NO(g) + O(g)
O3(g)
+ O3(g)
+ O3(g)
(III) CO(g) + OHH(g) + O2(g)
HO2 + NO(g)
NO2(g) + light energy
O(g) + O2(g)
For each mechanism, list the substance(s) that could have acted as a catalyst.
25
The reaction below was studied at 25 °C.
2I-(aq) + S2O82-(aq) 
I2(aq) + 2SO42-(aq)
The following data was collected:
Time (min)
0.0
0.2
0.4
0.6
0.8
1.0
[I-] (mol/L)
0.0800
0.0400
0.0200
0.0100
0.0050
0.0025
[I2] (mol/L)
0
a)
Complete the data table for I2(aq)
b)
Calculate the average rate of reaction for the production of I2(aq) over the course of
the time given.
551-534.E55
Question Booklet
Page 17
Part E
Questions 26, 27, 28 and 29 (Answer three questions only.)
If you answer all questions in this section, draw a line through the question that you
do not want to have corrected. If you do not questions 26, 27 and 28 will be corrected.
26
When 0.0150 mol NH3(g) and 0.0150 mol O2(g) are introduced into a 1.00 L container at a certain
temperature, the N2 concentration at equilibrium is 1.96  10-3 mol/L.
4 NH3(g) + 3 O2(g)  2 N2(g) + 6 H2O(g)
Calculate Kc for the reaction at this temperature.
27
A 0.15 mol/L solution of butanoic acid (CH3CH2CH2COOH) has a H3O+ concentration of
1.51  10-3 mol/L. A 0.035 mol/L solution of hydrofluoric acid (HF) has a OH concentration of
7.59  10-10 mol/L.
Which of the two acids is stronger?
Justify your answer using appropriate calculations.
28
29
A galvanic cell consists of a Mg electrode in a 1.0 mol/L Mg(NO3)2 solution and a Ag electrode
in a 1.0 mol/L AgNO3 solution.
a)
Draw a diagram of the cell specifying anode, cathode, and direction of electron flow.
b)
Calculate the standard cell potential of this electrochemical cell.
c)
Describe one method through which this cell potential may be increased.
A newly hired technician at a chemical factory was on night duty and had to decide whether the
following solutions could be pumped, one at a time, from one lab to another using copper, Cu,
pipes.
Iron nitrate
Lead nitrate
Silver nitrate
Fe(NO3)2
Pb(NO3)2
AgNO3
The technician decided to go ahead and pump the three solutions one at a time through the pipes,
flushing the pipes with water in between solutions to clean them.
Did the technician cause any chemical reactions to occur in the pipes?
Show your calculations and justify your answer.
551-534.E55
551-534
Chemistry
Comprehensive Exam
Number 55
Answer Booklet
Secondary 5
September, 2005
Student's Name
Group
Date
Answer Booklet
PART A
Questions 1 to 14
Blacken the letter that corresponds to your answer.
Each question is worth four marks.
1
[A] [B] [C] [D]
2
[A] [B] [C] [D]
3
[A] [B] [C] [D]
4
[A] [B] [C] [D]
5
[A] [B] [C] [D]
6
[A] [B] [C] [D]
7
[A] [B] [C] [D]
8
[A] [B] [C] [D]
9
[A] [B] [C] [D]
10
[A] [B] [C] [D]
11
[A] [B] [C] [D]
12
[A] [B] [C] [D]
13
[A] [B] [C] [D]
14
[A] [B] [C] [D]
551-534.E55
Page 1
Answer Booklet
Page 2
PART B
Questions 15, 16, 17 and 18
If you answer all questions in this section, draw a line through the question that you
do not want to have corrected. If you do not, questions 15, 16 and 17 will be
corrected.
15
SHOW ALL YOUR WORK
Answer: The ratio of the gas pressure in the 2nd container to the initial gas pressure in the
1st container is __________ :1.
4
551-534.E55
3
2
1
0
Answer Booklet
16
Page 3
SHOW ALL YOUR WORK
Answer: The volume of water vapour produced is _________________________.
4
551-534.E55
3
2
1
0
Answer Booklet
17
Page 4
SHOW ALL YOUR WORK
Answer: The unknown gas is most likely _________________________ because
__________________________________________________________________.
4
551-534.E55
3
2
1
0
Answer Booklet
18
Page 5
EXPLANATION
a)
b)
4
3
2
1
You have just finished Part B.
You should have answered three (3) questions.
If you have answered all four, draw a line through the question that you do not want to have
corrected.
551-534.E55
0
Answer Booklet
Page 6
PART C
Questions 19, 20, 21 and 22.
If you answer all questions in this section, draw a line through the question that you
do not want to have corrected. If you do not, questions 19, 20 and 21 will be
corrected.
19
SHOW ALL YOUR WORK
Answer: The specific heat capacity of the unknown metal is ____________________.
4
551-534.E55
3
2
1
0
Answer Booklet
20
Page 7
SHOW ALL YOUR WORK
Answer: The H for the neutralization of NaOH solution is ____________________.
4
551-534.E55
3
2
1
0
Answer Booklet
21
Page 8
SHOW ALL YOUR WORK
Answer: The H is ____________________.
4
551-534.E55
3
2
1
0
Answer Booklet
22
Page 9
SHOW ALL YOUR WORK
4
3
2
1
You have just finished Part C.
You should have answered three (3) questions.
If you have answered all four, draw a line through the question that you do not want to have
corrected.
551-534.E55
0
Answer Booklet
Page 10
PART D
Questions 23, 24 and 25.
If you answer all questions in this section, draw a line through the question that you
do not want to have corrected. If you do not, questions 23 and 24 will be corrected.
SHOW ALL YOUR WORK
Consumption of Nitrogen
Concentration (mol/L) of Nitrogen
23
4.50
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
0
10
20
30
40
50
60
70
Time (min)
Answer: The average rate of ammonia production is ____________________.
4
551-534.E55
3
2
1
0
Answer Booklet
24
Page 11
Answer:
Substance (s) that could have acted as catalysts
(I)
____________________________________________________________________.
(II)
____________________________________________________________________.
(III)
____________________________________________________________________.
4
25
3
2
1
0
SHOW ALL YOUR WORK
Rate calculation:
Answer:
Answer:
Time (min)
0.0
0.2
0.4
0.6
0.8
1.0
I (mol/L)
0.0800
0.0400
0.0200
0.0100
0.0050
0.0025
I2 (mol/L)
0
The average rate of reaction for the production of I2(aq) is _________________.
4
3
2
1
You have just finished Part D.
You should have answered two (2) questions.
If you have answered all three, draw a line through the question that you do not want to have
corrected.
551-534.E55
0
Answer Booklet
Page 12
PART E
Questions 26, 27, 28 and 29.
If you answer all questions in this section, draw a line through the question that you
do not want to have corrected. If you do not, questions 26, 27 and 28 will be
corrected.
26
SHOW ALL YOUR WORK
Answer: The Kc for the reaction at this temperature is ____________________.
4
551-534.E55
3
2
1
0
Answer Booklet
27
Page 13
SHOW ALL YOUR WORK
(Show all the work needed to solve the problem: explanations, formulas and calculations.)
Answer:
____________________ acid is the stronger of the two.
4
551-534.E55
3
2
1
0
Answer Booklet
28
Page 14
SHOW ALL YOUR WORK
a) Diagram
b) The standard cell potential is ____________________.
c) Method to increase the potential of the given cell.
4
551-534.E55
3
2
1
0
Answer Booklet
29
Page 15
SHOW ALL YOUR WORK
Answer:
The technician
did

did not
cause a chemical reaction to occur.

cause a chemical reaction to occur.
because _________________________________________________________
________________________________________________________________
4
3
2
1
You have just finished Part E.
You should have answered three (3) questions.
If you have answered all four, draw a line through the question that you do not want to have
corrected.
551-534.E55
0