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Iodination of acetone

الكلية كلية العلوم للبنات     القسم قسم الكيمياء     المرحلة 3
أستاذ المادة محمد هاشم مطلوب الغرابي       06/04/2018 06:22:44

KINETICS OF THE IODINATION OF ACETONE
Copyright: Department of Chemistry, University of Idaho, Moscow, ID 2014.
Read and/or review Section 13.3 in your textbook. Pay particular attention to Example 13.4.
Introduction
Solid iodine (I2) crystals have a dark red/black color. An aqueous iodine solution is yellow. When an aqueous
iodine solution reacts with acetone in the presence of an acid, the yellow color slowly fades as the iodine is
consumed. The products of the reaction are iodoacetone and hydrogen iodide. The hydrogen ion is a catalyst
for this reaction.
+
3 2 2 3 2
H
(CH ) C=O + I CH (CH I)C=O + HI
acetone + iodine iodoacetone + hydrogen iodide
?
?
The rate law for this reaction is of the form:
rate = k [I2]x [H+]y [(CH3)2C=O]z
The rate of this reaction will be followed by watching the solution s yellow color fade over time.
rate = - ?[I2 ]
?t
The rate law can be written as:
2 x + y z
2 32
rate = - ?[I ] = k [I ] [H ] [(CH ) C=O]
?t
In this experiment you will use the method of initial rates to determine the value of the rate constant, k, and the
orders of the reaction with respect to I2 (the value of x), H+ (the value of y), and (CH3)2C=O (the value of z).
You will perform four runs using different concentrations of reactants. For each run, you will produce an
Absorbance vs. Time plot. The slope of each plot can be used to find the initial rate of the reaction for that
particular run. This initial rate will be part of the data summarized in Table 2 of the Data and Analysis Sheet.
Since the iodine concentration is proportional to absorbance (A), we must also calculate the constant (b) relating
Absorbance to iodine concentration for your spectrometer using the following equation.
A = b [I2]
2
Because you are following the rate of the reaction by measuring the change in absorbance of the solution, you
will need to divide the change in absorbance vs. time by the constant b.
rate = - [I2 ] = - A
t b t
? ?
? ?
In this manner, the Absorbance vs. time plot can be used to obtain the initial rate of the reaction in concentration
per unit time.

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