Chemistry 12
1.
Which of the following units could be used to express the reaction rate?
A.
B.
C.
D.
2.
enthalpy.
activation energy.
the ΔH of the reaction.
the activated complex.
As an activated complex changes to products,
A.
B.
C
D.
5.
decreasing the [HCl].
increasing the temperature
increasing the volume of H2.
decreasing the surface area of Zn.
The statement, the minimum energy needed for a successful collision, defines
A.
B.
C.
D.
4.
mL/s
mL/g
g/mL
mL/mol
Consider the reaction:
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
The rate of production of ZnCl2, can be increased by
A.
B.
C.
D.
3.
Kinetics Practice Test # 2
potential energy changes to kinetic energy.
kinetic energy changes to potential energy.
kinetic energy changes to activation energy.
potential energy changes to activation energy.
Which of the following is most likely to have the greatest rate at room
temperature.
A.
B.
C.
D.
2H2(g) + O2(g) → 2H2O(l)
2Ag+(aq) + CrO42-(aq) → Ag2CrO4(s)
Pb(s) + 2HCl(aq) → PbCl2(aq) + H2(g)
CH4(g) + 2O2(g) → CO2(g) + H2O(g)
6
Consider the following PE diagram for an uncatalyzed and catalyzed reaction
PE
(kJ)
35kJ
10kJ
15kJ
Progress of the Reaction
Which of the following describes the forward catalyzed reaction?
Activation Energy (kJ)
A.
B.
C.
D.
7.
-15
15
-15
15
A substance that increases the rate of a reaction without appearing in the equation
for the overall reaction is a(an)
A.
B.
C.
D.
8.
10
10
25
25
ΔH (kJ)
product
catalyst
reactant
intermediate
Activation energy can be described as the
A.
B.
C.
D.
energy of motion
energy of the activated complex.
energy difference between the reactants and the products.
energy difference between the reactants and the activated complex.
9.
What effect does a catalyst have on a reaction?
It changes the ΔH of a reaction.
It increases the kinetic energy of the reactants.
It decreases the potential energy of the products.
It provides a reaction mechanism with a lower activation energy.
A.
B.
C.
D.
10.
Consider the following reaction involving 1.0 g of powdered zinc:
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
Trial
Temperature (0C)
Concentration of HCl
1
2
3
40
20
40
3.0
3.0
6.0
The rates in order of fastest to slowest are
A.
B.
C.
D.
11.
1, 2, 3
2, 1, 3
3, 1, 2
3, 2, 1
Consider the following potential energy diagram for a reversible reaction:
140
PE (kJ)
130
110
Progress of the reaction
Which of the following describes the system above?
A.
B.
C.
D.
Reaction
Activation Energy (kJ)
ΔH (kJ)
reverse
reverse
forward
forward
10
10
30
20
-20
-30
+10
+30
12.
An activated complex is a chemical species that is
A.
B.
C.
D.
13.
stable and has low PE.
stable and has high PE.
unstable and has low PE.
unstable and has high PE.
Consider the reaction: Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)
At a certain temperature, 2.05 g Ca reacts completely in 30.0 seconds. The rate of
consumption of Ca is
A.
B.
C.
D.
14.
15.
0.00208 mol/min
0.0833 mol/min
0.102 mol/min
5.00 mol/min
Increasing the temperature of a reaction increases the reaction rate by
I.
II.
III.
increasing frequency of collision
increasing the kinetic energy of collision
decreasing the potential energy of the collision
A.
B.
C.
D.
I only.
I and II only.
II and III only.
I, II, and III.
A certain reaction is able to proceed by various mechanisms. Each mechanism has
a different Ea and results in a different overall rate. Which of the following best
describes the relationship between the Ea values and the rates?
A.
B.
Ea
Ea
Rate
C.
Rate
D.
Ea
Rate
Ea
Rate
16.
For collisions to be successful, reactants must have
A.
B
C.
D.
17.
favourable geometry.
sufficient heat of reaction only.
sufficient potential energy only.
sufficient kinetic energy and favourable geometry.
Consider the following reaction: 1/2 H2(g) + 1/2 I2(g) → HI(g)
ΔH = +28 kJ
The activation energy for the formation of HI is 167 kJ. The activation energy for
the decomposition of HI is
A.
B.
C.
D.
18.
28 kJ
139 kJ
167 kJ
195 kJ
Which of the following factors affects the rate of heterogeneous reactions only?
A.
B.
C.
D.
nature of the reactant
temperature
surface area of reactants
concentration of reactants
19.
A 25.0 mL sample of hydrogen peroxide decomposes producing 50.0 mL of
oxygen gas in 137 s. The rate of formation of O2 in mL/min is
A.
B.
C.
D.
20.
0.182 mL/min
0.365 mL/min
10.9 mL/min
21.9 mL/min
Consider the following reaction mechanism:
step 1
step 2
In this reaction H2 is a
A.
B.
C.
D.
product
catalyst
reactant
reaction intermediate
2NO + H2 → N2 + H2O2
H2O2 + H2 → 2H2O
21.
Which of the following properties could be used to measure the rate of the
following reaction taking place in an open container?
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
A.
B.
C.
D.
22.
mass of Zn
solubility of HCl
concentration of Clcolour of the solution
Consider the following reaction: N2 + 3H2 → 2NH3
The rate of formation of NH3 is 3.0 mole/min. The rate of consumption of H2 is:
A.
B.
C.
D.
23.
1.5 mole/min
2.0 mole/min
4.5 mole/min
9.0 mole/min
Consider the following reaction mechanism:
NO2 + NO2 → N2O4
N2O4 + CO → CO2 + NO + NO2
Step 1
Step 2
In the overall reaction, N2O4 is a
A.
B.
C.
D.
24.
product
catalyst
reactant
reaction intermediate
Consider the following mechanism:
NO + O3 → NO2 + O2
O + NO2 → NO + O2
Step 1
Step 2
The catalyst is
A.
B.
C.
D.
O2
O3
NO
NO2
25.
Consider the following reaction: Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
The rate of this reaction increases when more Mg is added. This change is caused
by the
A.
B.
C.
D.
26.
addition of a catalyst
increase in surface area
change in the nature of the reactants
increase in concentration of reactants
Consider the following PE diagram
100
PE (kJ)
40
20
Progress of the reaction
The forward reaction can be described as
A.
B.
C.
D.
27.
H
Ea
Type
+20
+20
-20
-20
80
60
80
100
endothermic
exothermic
exothermic
endothermic
Consider the following reaction: HgO(s) → Hg(l) + 1/2O2(g)
The rate of this reaction can be expressed as
A.
B.
C.
D.
rate = [O2}1/2
rate = Δ[O2]/Δt
rate = Δ[Hg]/Δt
rate = Δ[HgO]/Δt
28.
Which of the following would react most rapidly?
A.
B.
C.
D.
29.
Powdered Zn in 1.0 M HCl at 25 0C
Powdered Zn in 20 M HCl at 40 0C
A lump of Zn in 2.0 M HCl at 25 0C
A lump of Zn in 1.0 M HCl at 40 0C
Addition of a catalyst to a reaction increases the rate because it
A.
B.
C.
D.
increases the value of ΔH
decreases the value of ΔH
provides an alternate mechanism with a lower Ea
provides an alternate mechanism with a higher Ea
30.
When a collision occurs between two reactant species which possess between
them the minimum kinetic energy a product does not always form. This may be a result
of
A.
B.
C.
D.
low temperature
small surface area
low concentrations
unfavourable geometry
Subjective Answers
1.
An experiment is done to determine the rate of the following reaction:
2Al(s) + 6HCl(aq) → 3H2(g) + 2AlCl3(aq)
The following data are collected
Time (s)
Mass of Flask + Contents (g)
0.0
30.0
60.0
270.230
270.200
270.170
60.0 s
0.060 g H2
270.170
Calculate the rate of consumption of Al in mol/min.
0.060 g H2
x
60.0 s
60 s
x
1 min
1mole H2
2.0 g
(3 marks)
x
2 mol Al
3 mol H2
= 0.020 mol Al/min
2.
Define the term activation energy.
The minimum energy required for a successful collision.
3.
Define the word Activated complex.
Unstable reaction intermediate with high potential energy and low kinetic
energy.
4.
Define the word mechanism.
A sequence of steps that determines the overall reaction.
5.
Consider the following reaction mechanism
Step 1
?
Step 2
H2 + Cl → HCl + H
Step 3
H + Cl2 → HCl + Cl
Step 4
Cl + Cl → Cl2
Overall
H2 + Cl2 → 2HCl
a)
Write the equation for step 1
Cl2
b)
2Cl
Identify the reaction intermediate(s)
Cl
6.
→
H
Consider the overall reaction: 4HBr + O2 → 2H2O + 2Br2
A proposed three-step mechanism is:
Step 1
HBr + O2 → HOOBr
Step 2
?
Step 3
HBr + HOBr → H2O + Br2
Write the equation for step 2.
2HBr + HOOBr → HOBr + H2O + Br2
7.
A student wishes to monitor the rate of the following reaction:
CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)
Identify two properties that could be used to monitor the rate of the reaction.
Describe and explain the changes that would occur.
Property 1
Mass of CaCO3(s)
Change and explanation
Decreases, as reactants are converted into
products.
Property 2
Concentration of HCl
Change and explanation
Decreases, as reactants are converted into
products.
Any two in this list!
Concentration of CaCl2(aq)
Increases, as reactants are converted into
products.
Volume of CO2
Increases, as reactants are converted into
products.
Mass of an open beaker
Decreases as CO2 escapes
Pressure of a closed system
Increases as CO2 is produced
8.
Carbon burns in air according to the following equation:
C(s) + O2(g) → CO2(g)
List four ways the rate of the above reaction could be increased.
Increase temperature
Increase the pressure
Increase O2 concentration
Add a catalyst
Increase C surface area
9.
Sketch the potential energy diagram for an endothermic reaction in the space
below. On your diagram clearly label:
i)
ii)
iii)
the energy of the activated complex
the activation energy
ΔH
PE
Ea
∆H
Progress of the Reaction