DRAFT: This module has unpublished changes.

Data Analysis and Conclusions

 

               After all data was collected, the rate constant for each reaction was easily obtained by calculating α (using the equation in the abstract section) and then plotting α against time. The slope of the straight line this graph creates is equal to the rate constant. All rate constants obtained for this experiment are shown in tabular format in the section named rate constants of reactions. As predicted, the rate of the Acetone Iodine reaction increased as the temperature was raised. At 35°C the rate constants are approximately ten times higher than the rate constants at 15°C which are ten times higher than the rate constants at 1°C. Therefore, this experiment proves that the Acetone Iodine reaction experiences a trend in which the rate constants of the reaction increase as temperature does.

 

                When comparing run 3 and 4 at each temperature, the hypothesis is supported. The only difference between run 3 and 4 is that run 4 has a higher concentration of acetone. As hypothesized, the rate constant from run 3 to run 4 decreases because the reaction occurs slower due to the higher amount of acetone. Run 4 occurs slower than run 3 because it has more acetone to transform into its enol form and then complex with iodine. This hypothesis is also supported when observing run 1 and 2 at 1°C the rate constant for run 1 is larger than that for run 2. In contrast, at 35 and 15°C the hypothesis is not supported because the rate constant for run 2 at these temperatures is higher than that for run 1. The concentration of acetone is higher in run 2 than run 1, so run 2 should occur slower. This deviation could have occurred due to the fact that water was present in run 1 but not in run 2.

 

                As the concentration of acid increased the reaction constant was predicted to increase. The acid is considered a catalyst and therefore and increase in acid concentration should directly relate to a increase in the rate of the reaction. This prediction was only supported by 4 examples. The only difference between run 1 and 3 is that 1 has a higher concentration of acid therefore run 1 should result in a faster reaction than run 3. This trend was observed at 15 and 1°C. Similarly, the only change from run 2 to run 4 is a decrease in the amount of acid, therefore run 2 should have a larger rate constant than run 4. This trend was observed at 15 and 35°C. The rest of the runs showed opposite results which can only be explained as experimental error. Also run 2 was the only run that did not have water present and there is a possibility this lack of water could have negatively affected the results.

 

                Like most experiments this lab contained some aspects of experimental error. Although the cell holder was flushed with nitrogen when at 1°C to prevent condensation on the cell wall, it is still possible that condensation occurred and therefore altered the absorbance observed creating error for the runs at 1°C. For each run the cell was only mixed for a few seconds by shaking the cell. There was no mixing that occurred as the reaction ran. This lack of mixing could have resulted in a reaction mixture that was not homogenous. If it was not homogeneous the rate of the reaction would be slowed. Another source of error could be that the cell was not kept in the cell holder when putting solutions into it. This lack of time in the cell holder could alter the temperature of the reaction and therefore affect the results. Overall this experiment successfully found the rate constant for the acetone iodine reaction at  three different temperatures and at 4 different concentrations of reagents. This experiment could have been improved in a few ways. First, the concentrations of the reagents could have been altered so that water was present in all runs. This alteration would reduce error for reactions occurring around the freezing point of water. Second, mixing could be introduced to the cell so that the reaction is homogeneous. Third, the cell could have been kept in the cell holder at all times to ensure that it is at the right temperature.

DRAFT: This module has unpublished changes.