CRIB
Kinetics
1. Consider the following rate equation:
−
d
[
A
]
dt
=
k
[
A
]
2
[
B
]
1/2
What is the order of the reaction with respect to A?
a.
0
b.
0.5
c.
1
d.
2
e.
2.5
Answer: d.
2. What kinetics are being followed for the rate of apple gathering in the following
situations?
Situation 1
:
You are picking apples from a single tree.
As you pick, the number of
available/reachable apples decreases, so the rate of apple picking decreases
proportionately.
Situation 2
:
You are walking through an orchard, picking apples as you go, at a constant
rate.
Situation 1
Situation 2
a.
0 order
1
st
order
b.
3
rd
order
pseudo1
st
order
c.
pseudo0 order
1
st
order
d.
1
st
order
pseudo0 order
e.
2
nd
order
1
st
order
Answer: d.
3. For a first order reaction, the rate constant is
k
= 3.8 x 10
8
s
1
. Calculate the half life of
the reaction.
a.
1.8 s
b.
1.8 min
c.
3.8 h
d.
5,066 hours
e.
7,310 hours
Answer: d.
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4. When formic acid (HCO
2
H) decomposes it follows first order kinetics:
HCO
2
H (g)
Æ
CO
2
(g) + H
2
(g)
The halflife of the reaction is 32 seconds. How many seconds are needed for formic
acid, initially 0.98 M to decrease to 0.06125 M?
a. 512 s
b. 64 s
c. 128 s
d. 54 s
e. 32 s
Answer: c. First figure out how many halflives need to have taken place in order for this
change in concentration to occur. The definition for a halflife is that half of the original
concentration is gone. We see that the concentration has dropped by a factor of 16.
Therefore four halflife periods have passed. So the time it takes to reach 0.06125 M is 32
sec * 4 =128 sec.
5. Consider an enzyme reaction for which V
max
is 9.4 x 10
3
M s
1
and the substrate
concentration happens to be equal to the Michaelis constant at 6.6 x 10
4
M. Calculate the
rate of the reaction, V.
a. 2.3 x 10
3
M s
1
b. 3.9 x 10
3
M s
1
c. 4.7 x 10
3
M s
1
d. 9.4 x 10
3
M s
1
e.
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 Spring '08
 ScottMcLuckey
 Electrochemistry, Oxidation Number, Kinetics, Redox, SCE

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