Niu (qn269) – Homework 8 – flowers – (53885)
1
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printout
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have
30
questions.
Multiplechoice questions may continue on
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before answering.
HW 8. Due 25 November 2008 at 11PM
001
10.0 points
The rate of formation of oxygen in the follow
ing reaction is 2.28 M/s.
2 N
2
O
5
(g)
→
4 NO
2
(g) + O
2
(g)
What is the rate of formation of NO
2
?
1.
1.14 M/s
2.
2.28 M/s
3.
9.12 M/s
correct
4.
0.57 M/s
5.
4.56 M/s
Explanation:
The NO
2
forms at 4
×
the rate of the O
2
.
002
10.0 points
Consider the reaction
2 NO
2
(g) + F
2
(g)
→
2 NO
2
F(g)
rate =
−
Δ[F
2
]
Δ
t
.
What is another form of the rate of the
reaction?
1.
Δ[NO
2
F]
Δ
t
2.
Δ[NO
2
F]
2 Δ
t
correct
3.
Δ[NO
2
]
2 Δ
t
4.
−
Δ[NO
2
]
Δ
t
5.
−
2 Δ[NO
2
]
Δ
t
Explanation:
003
10.0 points
Consider the concentrationtime dependence
as shown below for two first order reactions.
[A]
0
Molar Concentration
of Reactant
Concentration
−→
Time
−→
Which reaction has the greatest t
1
/
2
?
1.
the reaction represented by the lower
curve
2.
the reaction represented by the upper
curve
correct
3.
Unable to determine
Explanation:
004
10.0 points
One of the reactions used commercially to
produce hydrogen gas is
H
2
O(g) + CO(g)
→
H
2
(g) + CO
2
(g)
.
A proper expression for the rate of this
reaction could be
1.
−
Δ[CO
2
]
Δt
.
2.
+
Δ[CO]
Δt
.
3.
−
Δ[H
2
O]
Δt
.
correct
4.
−
Δ[H
2
]
Δt
.
Explanation:
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Niu (qn269) – Homework 8 – flowers – (53885)
2
The rate of a chemical reaction can either
be expressed as the rate of disappearance of
the reactant (as in this case) or as the rate
of the appearance of the product; however,
this rate is multiplied by the inverse of the
coefficient of the species in question.
The
negative sign here reminds us that as the
reaction progresses, this species is consumed
and goes down in concentration.
005
10.0 points
What is the rate for the formation of Cu(s) in
the reaction
Cu
2+
(aq) + H
2
(g)
⇀
↽
Cu(s) + 2 H
+
(aq)
if
Δ[H
+
]
Δ
t
= 1
.
2
×
10
−
3
?
1.
2
×
10
−
4
2.
2
.
4
×
10
−
3
3.
3
×
10
−
4
4.
1
.
2
×
10
−
3
5.
6
×
10
−
4
correct
Explanation:
006
10.0 points
What is the rate law for the reaction
A + B + C
→
D
if the following data were collected?
Exp
[A]
0
[B]
0
[C]
0
Initial Rate
1
0.4
1.2
0.7
2
.
32
×
10
−
3
2
1.3
1.2
0.9
7
.
54
×
10
−
3
3
0.4
4.1
0.8
9
.
25
×
10
−
2
4
1.3
1.2
0.2
7
.
54
×
10
−
3
1.
rate = 3
.
36
×
10
−
3
[A]
1
[B]
3
[C]
0
correct
2.
rate = 1
.
79
×
10
−
3
[A]
0
[B]
2
[C]
1
3.
rate = 1
.
49
×
10
−
3
[A]
0
[B]
3
[C]
1
4.
rate = 4
.
48
×
10
−
3
[A]
1
[B]
2
[C]
1
5.
rate = 5
.
37
×
10
−
3
[A]
1
[B]
3
[C]
0
Explanation:
007
10.0 points
For a given reaction, the ratelaw is
1.
an equation in which reaction rate is equal
to a mathematical expression involving con
centrations of reactants.
correct
2.
a constant of proportionality between re
action rate and the concentrations of reac
tants.
3.
the sum of the powers to which reactant
concentrations appear.
Explanation:
The rate law for a reaction
A + B
→
C + D
is set up as
Rate =
k
[A]
x
[B]
y
This is an expression involving the con
centrations. The constant of proportionality
option is the rate constant
k
, while the sum
of powers option is the order of reaction.
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 Fall '08
 FLOWERS
 Rate equation

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