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Physical Chemistry I - Kinetics Practice Problems for CHEM 3410 at Stockton College - Prof, Assignments of Physical Chemistry

Practice problems on chemical kinetics for students enrolled in chem 3410 at the richard stockton college of new jersey. The problems involve deriving rate laws for reversible and irreversible reactions, as well as determining the apparent orders of reactions based on rate constants.

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Pre 2010

Uploaded on 08/08/2009

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The Richard Stockton College of New Jersey
Chemistry Program, School of Natural Sciences and Mathematics
PO Box 195, Pomoma, NJ
CHEM 3410: Physical Chemistry I โ€” Fall 2008
Kinetics practice problems
November 21, 2008
1. The formation of HI from H2and I2can be described by reversible second order kinetics.
H2+I2*
)2HI
However, direct bimolecular reaction between H2and I2is not observed to occur. A proposed
mechanism for the forward reaction is:
I2*
)2I(1)
H2+ 2 Iโ†’2HI (2)
(a) Derive a rate law assuming that step (1) is reversible, step (2) is irreversible and step (2) is
the slowest process.
(b) Derive a rate law assuming that step (1) is reversible, step (2) is irreversible and step (2) is
the fastest process. You can use the steady-state approximation for the concentration of the
intermediate [I].
Hint: For both parts, be sure to pay careful attention to the stoichiometry of the proposed elementary
reactions.
2. Consider the reaction:
2A+Bโ†’D
Suppose that the mechanism of this reaction is found to consist of the following elementary reac-
tions:
A+B
k1
EGGGGGG
GGGGGGC
kโˆ’1
C
A+C
k2
GGGGGGA
D
(a) Show that this mechanism is consistent with the overall reaction.
(b) Write expressions for d[C]
dt and d[D]
dt in terms of [A], [B], [C], [D], k1,kโˆ’1, and k2.
(c) Impose the steady-state approximation and solve for [C]ss.
(d) Use the steady-state approximation to derive the rate law for d[D]
dt in terms of [A], [B], k1,
kโˆ’1, and k2.
(e) If k2[A]๎˜kโˆ’1what are the apparent orders of the reaction with respect to [A] and [B]?
(f) If k2[A]๎˜œkโˆ’1what are the apparent orders of the reaction with respect to [A] and [B]?

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The Richard Stockton College of New Jersey

Chemistry Program, School of Natural Sciences and Mathematics PO Box 195, Pomoma, NJ

CHEM 3410: Physical Chemistry I โ€” Fall 2008

Kinetics practice problems

November 21, 2008

  1. The formation of HI from H 2 and I 2 can be described by reversible second order kinetics.

H 2 + I 2 โ‡€โ†ฝ 2 HI

However, direct bimolecular reaction between H 2 and I 2 is not observed to occur. A proposed mechanism for the forward reaction is: I 2 โ‡€โ†ฝ 2 I (1) H 2 + 2 I โ†’ 2 HI (2)

(a) Derive a rate law assuming that step (1) is reversible, step (2) is irreversible and step (2) is the slowest process. (b) Derive a rate law assuming that step (1) is reversible, step (2) is irreversible and step (2) is the fastest process. You can use the steady-state approximation for the concentration of the intermediate [I].

Hint: For both parts, be sure to pay careful attention to the stoichiometry of the proposed elementary reactions.

  1. Consider the reaction: 2 A + B โ†’ D

Suppose that the mechanism of this reaction is found to consist of the following elementary reac- tions: A + B

k 1 EGGGGGGGGGGCGG kโˆ’ 1

C

A + C

k 2 GGGGGGA D

(a) Show that this mechanism is consistent with the overall reaction. (b) Write expressions for d dt[C ]and d[ dtD ]in terms of [A], [B], [C], [D], k 1 , kโˆ’ 1 , and k 2. (c) Impose the steady-state approximation and solve for [C]ss. (d) Use the steady-state approximation to derive the rate law for d[ dtD ] in terms of [A], [B], k 1 , kโˆ’ 1 , and k 2. (e) If k 2 [A]  kโˆ’ 1 what are the apparent orders of the reaction with respect to [A] and [B]? (f) If k 2 [A]  kโˆ’ 1 what are the apparent orders of the reaction with respect to [A] and [B]?