Version 206 – Quiz 5 – VANDEN BOUT – (53585)
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001
10.0 points
Consider the irreversible reaction
A + 2 B
→
3 C
.
Which of the following correctly expresses
the rate of change of [B] ?
1.
Δ[B]
Δ
t
=

1
2
(rate of rxn)
2.
Δ[B]
Δ
t
=

2 (rate of rxn)
correct
3.
Δ[B]
Δ
t
= +(rate of rxn)
4.
Δ[B]
Δ
t
=

(rate of rxn)
5.
Δ[B]
Δ
t
= +2 (rate of rxn)
6.
Δ[B]
Δ
t
= +
1
2
(rate of rxn)
Explanation:
As B is a reactant and consequently disap
pears during the reaction, its rate of change
will be negative and the inverse of the coeffi
cient is used when writing the rate:
(rate of rxn) =

1
2
Δ[B]
Δ
t

2 (rate of rxn) =
Δ[B]
Δ
t
002
10.0 points
The reaction
2 N
2
O
5
→
2 N
2
O
4
+ O
2
is first order.
At a certain temperature it
has a rate constant of 0.0840 sec
−
1
.
At this
temperature, how long would it take for 95%
of a given sample to decompose?
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 Spring '07
 Holcombe
 Chemistry, Reaction, Chemical reaction, Rate equation

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