CHEM_100_11 2013
Assignment #5 Due to Jan. 30
KINETICS
(chapter 14)
1. {14} Indicate the order ( zero, 1st or 2nd)
of the rxn Aà B for each of the following observations
a) A plot of the inverse of the concentration
[A] versus time yields a straight line
b) The
unit of rate constant is M×s-1
c) The rxn has a half-life that is independent of the initial
concentration, [A]0
d) the concentration of reactant [A] fall to
one-half in equal intervals of time
e) the half-life of the rxn gets shorter as
the initial concentration is increased
f) A
plot of the ln [A]
versus time yields a straight line
g) When the initial concentration [A] doubles,
the rate doubles.
h) When [A] is reduced by a factor of 2, the
rate of the reaction is reduced by a factor of 4.
i)
Change
in [A] does not change the rate
j) the unit of the rate constant is M-1s-1
k) the unit of the rate constant is s-1
l)
the rate law
is described by the formula : rate=k[A]2
m) A plot of [A]
versus time yields a straight line.
n) The rate law is
described by the formula rate=k
2. {10} The data in the table below were
obtained using the initial rate method for the reaction:
2ClO2 (aq)
+ 2OH- (aq) à
ClO3- (aq) + ClO2-(aq) + H2O (l)
exp. number [ClO2],
M [
1 0.060 0.030 0.0248
2 0.020 0.030 0.00276
3 0.020 0.090 0.00828
a) {5} analyze data and deduce the
differential rate law
b) {2} calculate the value of the rate
constant (with units!)
c) {1} what is the overall order of this
reaction?
d) {2} calculate the reaction rate for [ClO2]=[OH-]=
0.01M
3. {10}
The first-order rate constant for the reaction of methyl chloride (CH3Cl)
with water to produce methanol (CH3OH) and hydrochloric acid (HCl) is 3.32 x 10-10 s-1 at 25 oC. Calculate the rate constant at 40oC
if the activation energy is 116 kJ/mol.
4. {10} Consider the first-order reaction Aà
product, with k=2.95 x 10-3 s-1. What percent of A remains after 100 s?
5. {10} the reaction 2Aà B is second order with
a rate constant of 52 M-1 min-1 at 25oC.
(a) {5} Starting with [A]0
= 0.0082M, how long will it take for [A]t = 2.7 x 10-7 M?
(b) {5} Calculate the
half-life of this reaction.
6. {15} The reaction Aà
2B + C is first order. If the initial [A] =1.50 M and k=1.02 x10-3 s-1,
(a) {10} what is the value of [A] after 400
s?
(b) {5} What is
the concentration of B after the 400 s? Assume that volume is constant during
the rxn.
7. {5} The reaction 2Aà B is first order in A
with a rate constant of 1.5 x 10-2 s-1 at 100oC.
How long (in seconds) will it take for A to decrease from 0.30M to 0.10 M?
8. {6} For the elementary process N2O5
(g) à NO2(g)
+ NO3(g) the activation energy , Ea,
is 154kJ/mol and
overall ΔE reaction is 136 kJ/mol.
(a). {2} Sketch
the energy profile for this reaction, and label Ea and ΔE.
(b) {2} What is
the activation energy for the reverse reaction?
(c) {2} Which reaction
is faster, forward or reverse?
9. {10} Understanding the high-temperature
behavior of nitrogen oxides is essential for controlling pollution generated in
automobile engines. The decomposition of NO to N2 and O2
is second order with rate constant of 0.0796 M-1s-1 at
737 0C and 0.0815 M-1s-1 at 947 0C.
Calculate the activation energy for the reaction.