Rate Law Lab Report #3 PDF

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Rate Law By: Jonathan Martinez

Abstract This laboratory experiment is composed of 2 parts. In this experiment the rate law of the reaction 2 I–(aq) + H2O2 (aq) → I2 (aq) + 2 H2O (l). In order to determine if the change in temperature has an effect on the rate of the reaction. The rate of the reaction was found to be rate = k [I–]p [H2O2]q

Introduction The rate of a reaction depends on a few factors such as temperature, concentration and presence of catalysts. In this experiment the rate of reaction was determined by the amount of I2 formed. In this experiment the use of chemical kinetics (study of the rate under different conditions).the rate law of this reaction is found by the information given such as the different concentrations at different times. The rate law was determined experimentally after looking at the initial concentrations of the reactants. The rate is given by rate = k [A]p [B]q [C]r. A,B, and C, are the reactants and p,q,r are the individual orders. In this case only A and B were used therefore only the individual orders for p and q were found. In order to find p and q one of the concentrations needs to stay constant and the other one is changed. When the values of A and B are found the value of k can be calculated by using every one of the individual reactions and taking the average.

Procedure In order to get the rate law for this experiment it was necessary to do numerous steps. First a solution of potassium iodide (KI) and hydrogen peroxide (H2O2) were made. It was also necessary to stabilize the solution with an [H+] buffer,starch solution (indicator) and sodium thiosulfate (Na2S2O3) as a source of thiosulfate ion. The solution also contained distilled water in order to the final volume to reach 40.00 ml. For each of the trials a solution was made and placed in a flask being careful so that no O2 interferes with the reaction. Once the second solution is added to the flask the solutions must be swirl until the solution turns blue. The time that it took for the solution to change in color must be measured. This process was repeated 5 times in order to get the 3 points of determination of p and q. In this experiment it was concluded that both p and q are first order reactions. In the second part of this experiment the temperature was tested to determine the relation that it has in the rate of the reaction. This time solutions A and B were mixed together at different temperatures to indicate whether or not the temperature affects the reaction rate.

Results & Discussion So luti on #

Moles (S2O3 )2-

Moles of I2

[I2]

Rate M/s

1

0.0001

0.00005

0.00125 2.13E-6

2

0.0001

0.00005

3

0.0001

4

[I-]0

ln[I-]

[H2O 2]0

ln[H2 O2]0

ln(rate K )

0.015 -4.199

0.015

-4.199

-13.06 0.0095

0.00125 4.14E-6

0.03

-3.51

0.015

-4.199

-12.39 0.0092

0.00005

0.00125 6.28E-6

0.045 -3.10

0.015

-4.199

-11.98

0.0093

0.0001

0.00005

0.00125 1.06E-5

0.045 -3.10

0.025

-3.68

-11.45

0.0094

5

0.0001

0.00005

0.00125 1.44E-5

0.045 -3.10

0.035

-3.35

-11.15

0.0097

K

A

v

e

r

a

g

e

Sol Moles uti (S2O3) on 2-

Moles of I2

[I2]

Rate M/s

[I-]0

[H2O 2]o

ln(rate )

1

0.0001

0.00005

0.00125 7.27E-6

0.045 0.015

-11.83

2

0.0001

0.00005

0.00125 1.25E-5

0.030 0.015

3

0.0001

0.00005

0.00125 7.49E-6

4

0.0001

0.00005

5

0.0001

6

0.0001

0.00927 M/s

ln(k)

1/T

0.0108

-4.53

1/313

-11.29

0.0278

-3.58

1/313

0.015 0.015

-11.80

0.0333

-3.40

1/303

0.00125 9.77E-6

0.030 0.015

-11.54

0.0217

-3.83

1/303

0.00005

0.00125 1.82E-5

0.045 0.025

-13.22

0.00162

-6.43

1/273

0.00005

0.00125 2.30E-6

0.045 0.035

-12.98

0.00146

-6.53

1/273

Conclusion

K

A series of different reactions were carried out to determine the kinetic properties of rate laws. In this experiment the rate was determined by the change in color from clear to blue over a certain amount of time. Both of the individual reactions were (KI) and (H2O2) are first order and therefore the overall reaction is second order....