Kinetics Reaction Order Reaction Rates Rate Constant
Obtain the Excel spreadsheet that goes with this activity
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The spreadsheet has two columns for you to enter data obtained from an experiment measuring the
change of concentration over time.
By analyzing the three graphs produced you can determine the order of the reaction and values for the
rate constant (k)
Blue Line is the graph specified in the title. The black line is a trend line (calculated by least squares analysis)
The trend line is used to calculate the linear equation for the data selected. You will want to use the graph with
the trend line that matches the graphed data-- the data line may be obscured by the trend line. If the trend line
lies over the line of the data graphed is means the linear equation accurately matches the data graphed.
The linear equation for the trend line is shown under the title of each graph.
y=mx=b
m=slope
Reaction Order Summary---study this summary to understand how to graphically determine the order of a
reaction.
Zero Order Reactions
Graphical characteristics
A plot of concentration of reactant vs time results in a straight line with a negative slope
k = -slope
Rate = k
Rate law for Zero Order Reactions
(The rate of the reaction does not depend on the concentration or the reactants)
First Order Reactions
Graphical characteristics
A plot of natural log of the concentration of reactant vs time results in a straight line with a
negative slope
k = -slope
Rate law for First Order Reactions
-
ln [A]t = kt + ln [A]0
y = mx + b
---equation of a straight line
(Concentration doubles—rate of reaction doubles)
Second Order Reactions
Graphical characteristics
A plot of the reciprocal of the concentration ( 1/[A] ) of reactant vs time results in a straight line
with a positive slope
k = slope
Rate law for second Order Reactions
1
1
 kt 
[ A] t
[ A] 0
y =mx + b
---equation of a straight line
(Concentration doubles—rate of reaction doubles)
Problem #1
graph decomposition of hydrogen peroxide
2 H2O2  2 H2O + O2
Identify order of reaction
time
What is value of k for reaction?
0
300
600
1200
1800
3000
[H2O2]
2.32
1.86
1.49
0.98
0.62
0.25
write the rate law for the reaction
Problem #2
Graph reaction of Buckminsterfullerene
C60O3  C60O + O2
Identify order of reaction
What is value of k for reaction?
Write the rate law for the reaction
Problem #3
Solutions of A=H3COC6H4CNO in carbon tetrachloride
dimerize slowly as shown by the following data
Identify order of reaction
What is value of k for reaction?
Write the rate law for the reaction
Time
min
3
9
15
21
27
33
39
45
51
57
63
69
75
[C60O3]
0.04241
0.03634
0.03121
0.0268
0.02311
0.01992
0.01721
0.01484
0.01286
0.01106
0.00955
0.00827
0.0071
Time
Hrs
0
3.5
7
10.5
14
17.5
21
24.5
28
31.5
35
H3COC6H4CNO
0.995
0.745
0.595
0.494
0.424
0.37
0.331
0.295
0.27
0.247
0.229
Problem #4
Identify order of reaction
What is value of k for reaction?
Write the rate law for the reaction
Time
Sec
0
1
2
3
4
5
6
[A]
8
7.33
6.66
5.99
5.332
4.665
3.998
Problem 1
Use the rate law to determine the time when half of the reactant has been used up
Problem 2
Use the rate law to determine the time when half of the reactant has been used up
Problem 3
Use the rate law to determine the time when half of the reactant has been used up
Problem 4
Use the rate law to determine the time when half of the reactant has been used up