Kinetics
Quiz #5
Mechanisms
Answers
1. Consider the following reaction mechanism
Step 1: M + X → MX
Step 2: MX + A → D + X
The chemical species MX is a(n)
A.
B.
C.
D.
Catalyst
Inhibitor
Final Product
Reaction Intermediate
2. Consider the following reaction mechanism
Step 1: NO2 + NO2 → NO + NO3
Step 2: NO3 + CO → NO2 + CO2
The overall reaction is
A.
B.
C.
D.
2NO2 → NO3 + NO
NO2 + CO → NO + CO2
NO3 + CO → NO2 + CO2
NO2 + NO3 + CO → NO3 + NO2 + NO + CO2
3. Consider the following reaction mechanism
Step 1: V3+ + Cu2+ → V4+ + Cu+
(slow)
Step 2: Cu+ + Fe3+ → Cu2+ + Fe2+ (fast)
The reaction intermediate is
A.
B.
C.
D.
Cu+
Cu2+
V3+
Fe3+
4. Consider the following reaction Mechanism
Step 1: H2O2 + I - → H2O + IOStep 2: H2O2 + IO - → H2O + O2 + I The reaction intermediate is
A.
B.
C.
D.
IIO H2O
H2O2
5. Consider the following potential energy diagram
PE
(KJ)
Progress of the reaction
The above potential energy diagram represents an
A.
B.
C.
D.
Exothermic reaction involving one step
Exothermic reaction involving two steps
Endothermic reaction involving one step
Endothermic reaction involving two steps
6. Consider the following reaction mechanism
Step 1: NO2(g) + NO2(g) → NO(g) + NO3(g) (slow)
Step 2: NO3(g) + CO(g) → CO2(g) + NO2(g) (fast)
Which one of the following changes would result in the greatest increase in reaction rate
A.
B.
C.
D.
Increase [CO]
Decrease [NO]
Increase [NO2]
Increase [NO3]
7. An uncatalyzed reaction was found to produce 40 kJ of energy in 10 mins. When
catalyzed, the same reaction produced 40 kJ of energy in 2 mins. Which one of the
following potential energy diagrams is consistent with the above data?
PE
A
B
PE
Reaction Path
C
PE
Reaction Path
D
Reaction Path
PE
Reaction Path
8. Consider the following reaction mechanism
Step 1: ICl + H2 → HI + HCl (slow)
Step 2: ICl + HI → HCl + I2 (fast)
The Species HCl is a
A.
B.
C.
D.
Product
Catalyst
Reactant
Reaction Intermediate
9. Consider the following reaction mechanism
Step 1: Cl(g) + O3(g) → ClO(g) + O2(g)
Step 2: O(g) + ClO(g) → Cl(g) + O2(g)
The Reaction intermediate is
A.
B.
C.
D.
Cl
O2
O3
ClO
10. In a reaction mechanism, the rate determining step is the
A.
B.
C.
D.
Fastest and has the lowest reaction rate.
Fastest and has the highest activation energy
Slowest and has the lowest activation energy
Slowest and has the highest activation energy
PE
Reaction Progress
11. Select the true statement concerning the above potential energy diagram.
The catalyzed reaction has a larger ∆H
The uncatalyzed reaction has a larger ∆H
The catalyzed reaction has a greater rate of reaction
The uncatalyzed reaction has a greater rate of reaction
A.
B.
C.
D.
12. Which point on the diagram above represents the potential energy of the activated
complex formed in the uncatalyzed reaction?
I
II
A.
B.
C.
D.
III
IV
I
II
III
IV
13. Consider the following reaction
Step 1: NO(g) + O3(g) ------ > NO2(g) + O2(g)
Step 2: O(g) + NO2(g) ------ > NO(g) + O2(g)
The catalyst is
A.
B.
C.
D.
O2
O3
NO
NO2
14. Consider the following reaction mechanism
Step 1: N2O(g) ------ > N2(g) + O(g)
Step 2: N2O(g) + O(g) ------ > N2(g) + O2(g)
The reactant in the overall reaction is
A.
O
B.
C.
D.
O2
N2
N2O
15. Consider the following reaction
O3(g) + NO(g) ----- > NO2(g) + O2(g)
NO2(g) + O(g) ------ > NO(g) + O2(g)
The product in the overall reaction is
A.
B.
C.
D.
O2
O3
NO
NO2
Use the following reaction mechanism to answer questions 16 and 17.
Step 1:
2PO
→
P2O2
(fast)
Step 2:
P2O2 +
H2
→
P2O + H2O
(slow)
Step 3:
P2O +
H2
→
P2
+ H2O
(fast)
16.
Increasing the concentration of which of the following substances would cause
the greatest increase in the reaction rate?
A.
H2
B.
PO
C.
P2O
D.
H2O
17.
Which of the following are products in the overall reaction?
I
P2
II
P2O2
III
PO2
IV
H2O
A.
I and II only
B.
I and IV only
C.
II and III only
D.
III and IV only
18.
The Intermediates are:
A.
NO
H2
B.
H2O
P2
C.
P2O2
PO
D.
P2O2
P2O
19.
Which of the following could describe a catalyst?
A.
A substance that increases the reaction time.
B.
A substance that provides an alternate mechanism with higher activation
energy.
C.
A substance that is formed in one step and used up in a subsequent step in
a reaction mechanism.
D.
A substance that is used up in one step and reformed in a subsequent
step in a reaction mechanism.
20.
Consider the following reaction:
2PO(g) + O2(g) → 2PO2(g)
Why would this reaction probably involve more than one step?
A.
There is insufficient activation energy.
B.
This reaction has high activation energy.
C.
Reactions between gases are typically slow.
D.
A successful collision between three molecules is unlikely.
21.
Consider the following reaction mechanism:
Step 1
Cl3 → Cl2 + Cl
Step 2
Cl3
+ Cl →
2Cl2
Which of the following could represent the activated complex for Step 2?
A.
Cl
B.
Cl2
C.
Cl3
D.
Cl4
Consider the reaction: 2C4H10(g) + 13O2(g) → 8CO2(g) + 10H2O(l)
Which of the following explains, in terms of collision theory, why this reaction
occurs in more than one step?
A.
a low C4H12(g) pressure
B.
low temperature of reactant mixture
C.
low probability of a multi-particle collision
D.
particles collide with insufficient kinetic energy
22.
23.
Consider the following reaction mechanism and overall reaction:
Step 1
½ O2(g) + NO(g)
→ NO2(g)
sunlight
Step 2
Step 3
O2(g)
NO2(g)
+ O(g) →
→
O3(g)
Overall
3/2 O2 (g)
→
What is the catalyst in this mechanism?
A.
O
B.
NO
C.
NO2
D.
sunlight
NO(g)
O3(g)
+ O(g)
24.
What is an intermediate in this mechanism?
A.
O
B.
NO
C.
O3
D.
sunlight
25.
Consider the following reaction mechanism:
Step 1
NOI
→
NO
Step 2
NOI
+ I
→ NOI2
Identify the reaction intermediate.
A.
I
B.
NOI2
C.
NO
D.
NOI
26.
Consider the following reaction mechanism:
Step 1
2NO2 →
NO3 +
NO
Step 2
NO3 + CO
→
NO2 + CO2
Identify a product in the overall reaction.
A.
CO
B.
CO2
C.
NO2
D.
NO3
27.
Consider the following reaction mechanism:
Step 1
2NO2 →
NO3 +
NO
Step 2
NO3 + CO
→
NO2 + CO2
Identify an intermediate.
A.
CO
B.
CO2
C.
NO2
D.
NO3
+
I