# Temperature and Reaction Rate ```CHM 101/102
Temperature and Reaction Rate
General Chemistry 101/102
Laboratory Manual
University of North Carolina at Wilmington
Laboratory Manual
CHM 101/102
Temperature and Reaction Rate
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Purpose
 To study the effect of temperature on the reaction
rate and the reaction rate constant (k) of a chemical
reaction and to determine the value of the activation
energy (Ea) for the reaction.
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Safety Considerations
 Wash your hands thoroughly after handling
chemical reagents and before leaving the lab.
 All chemical wastes should be placed in the
labeled jar in the hood.
Laboratory Manual
CHM 101/102
Temperature and Reaction Rate
•
Background
 The chemical reaction being studied in this
experiment is:
6 I- + BrO3- + 6 H+
3 I2 + Br - + 3 H2O
bromate ion
 In the previous experiment, you determined the
rate law for this reaction to be:
Rate = k [I-] [BrO3-] [H+]2
 The value of the rate constant (k) depends on the
temperature. The relationship between rate constant
and temperature is given by the Arrhenius Equation
k = Ae-Ea/RT
Laboratory Manual
CHM 101/102
Temperature and Reaction Rate
•
Background
rate constant
activation
energy
k = Ae-Ea/RT
frequency
factor
temperature (K)
Idea Gas constant
(8.31 J/K&middot;mol)
 Taking the log of both sides of the Arrhenius
Equation transforms it into a linear equation:
ln k = - Ea + ln A
RT
Laboratory Manual
CHM 101/102
Temperature and Reaction Rate
•
Background
 The activation energy for a reaction can be found
by measuring the value of k at several different
temperatures and then plotting ln k vs. 1/T
ln A
Laboratory Manual
CHM 101/102
Temperature and Reaction Rate
•
Procedure
 Each trial is performed at a different temperature
(approximately 0 &ordm;C, 10 &ordm;C, 25 &ordm;C, and 40 &ordm;C).
 Measure the quantities shown in Table 1 into flasks
labeled “A” and “B”.
B
 Allow both flasks to reach the desired temperature
at the desired temperature during the reaction.
Record the time it takes for the blue color to appear.
Laboratory Manual
CHM 101/102
Temperature and Reaction Rate
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Calculations
 A sample calculation for k is shown below.
-5 M
3.3
x
10
Rate =
= k [I-] [BrO3-] [H+]2
Dt
3.3 x 10-5 M
k=
Dt [I-][BrO3-][H+]2
3.3 x 10-5 M
k=
(180 s)(0.0020 M)(0.0080 M)(.020 M)2
k = 29 L3/mol3&middot;s
Laboratory Manual
CHM 101/102
Temperature and Reaction Rate
•
Calculations