Experiment 16: Kintics: the Iodine Clock

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Experiment 16: Kinetics: The Iodine Clock
Jane Smith

Purpose:
The objective of this experiment was for students to apply their knowledge of kinetics and rate laws in order to determine the rate of a chemical reactions, activation energy, and frequency factors of those reactions. Specifically, this experiment was performed using a series of solutions with varying concentrations of KI, Na2S2O3, and (NH4)2S2O3 . Students recorded time elapsed to observe physical evidence of a reaction taking place in a solution. The time elapsed during the reaction was recorded during the experiment, while the rate (M/sec), reaction constant, and activation energies were calculated post-lab.

Data:Reaction Rates and Concentrations
Run #| [KI] (M)| [Na2S2O3] (M)| [(NH4)2S2O8] (M)| Time (sec)| Rate of rxn (M/sec)| Temp. (K)| K | 1| 0.075| 0.00044| 0.0190| 46.2| 9.5x10-6| 296| 0.088| 2| 0.050| 0.00044| 0.0190| 90.7| 4.8x10-6| 296| 0.101| 3| 0.025| 0.00044| 0.0190| 342.5| 1.3x10-6| 296| 0.109| 4| 0.075| 0.00044| 0.0120| 76.7| 5.7x10-6| 296| 0.084| 5| 0.075| 0.00044| 0.0062| 183.6| 2.4x10-6| 296| 0.069| 6| 0.075| 0.00044| 0.0190| 15.0| 2.9x10-5| 309| 0.271| 7| 0.075| 0.00044| 0.0190| 171.3| 2.6x10-6| 278| 0.024| 8| 0.075| 0.00022| 0.0190| 24.8| 8.9x10-6| 296| 0.083|

Runs and Activation energies
Run| J/ mol K|
1| 136.00|
2| 203.08|
3| 390.67|
4| 250.48|
5| 734.57|
6| 120.43|
7| 3130.8|
8| 279.95|

m= 1.819= approx 2
n=1.233= approx 1

Calculations
Run #1: 
30 mL of 0.20 M KI 
20 mL of 0.00175 M Na2S2O3 
00 mL of water 
0.15 mL (3 drops) of starch solution 
30 mL of 0.050 (NH4)2S2O8 

[KI]= (0.03L *0.2 M)/(0.03 L KI+ 0.02L Na2S2O3 +0 L water+ 0.00015 L starch +.03 L (NH4)2S2O8) = 0.075 M

[Na2S2O3]= (0.02L *0.00175 M)/(0.03 L KI+ 0.02L Na2S2O3 +0 L water+ 0.00015 L starch +.03 L (NH4)2S2O8) =0.00044 M

[(NH4)2S2O8]= (0.03L *0.05 M)/(0.03...
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