Determination of Rate and Order of a Reaction

Topics: Rate equation, Order of reaction, Chemical reaction Pages: 4 (1206 words) Published: September 26, 2012
Determination of Rate and Order of a Reaction
This experiment used a spectrometer to find the wavelength with maximum absorbance in a green food coloring solution. For this particular solution the wavelength was 629.7 nm. The system was then calibrated to that and was set to measure the food coloring and bleach solution. The measured visible light absorbance of the mixed solution was collected over a time of 200 seconds and eight points were then selected and placed into the Absorbance Spectrum Data Table. The table shows that over time the absorption is decreasing.

Absorbance Spectrum Data Table:
Time| A| [FC]| LN [FC]| 1/[FC]|
0| 1.04| 0.00063| -7.36931| 1586.538|
25| 0.726| 0.00044| -7.72874| 2272.727|
50| 0.481| 0.000292| -8.14042| 3430.353|
101| 0.209| 0.000127| -8.97395| 7894.737|
126| 0.142| 8.61E-05| -9.36046| 11619.72|
151| 0.099| 0.00006| -9.72117| 16666.67|
175| 0.072| 4.36E-05| -10.0396| 22916.67|
200| 0.054| 3.27E-05| -10.3273| 30555.56|

A graph, Absorption vs. time, was created from the time and absorption points chosen from all the data collected over the entire 200 seconds. As with the chart, it can be seen in the Absorption vs. time graph that light absorbed in the food coloring over time decreases.

To find the concentration of the solution the equation for Beer’s law was used. Knowing A, є, and b, it was possible to solve for c and graph the points in the Concentration vs. time graph. This graph shows that over time the concentration of the food coloring is decreasing in the bleach. This function is for a zero-order reaction, and as it was not linear, it is not a zero-order reaction.

The natural log of the concentration is for a first order reaction. The ln of concentration was taken in the Absorbance Spectrum Data table to create the graph of Ln Concentration vs. time. This graph displays a linear line, which means that the reaction is a First-order...
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