8 be very careful to keep up with the dilution factor

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8.Be very careful to keep up with the dilution factor for the unknown. You can’t solve the problem without it. We all should have ppmxxyyiifi00.109000.0Procedure – Collecting data9.When you have 10 labeled and prepared test tubes, bring them (which includes ablank) to the UV-Vis spectrophotometer for analysis.10.To minimize experimental uncertainty and variability, we must all use the same spectrometer. Do not come to the instrument until all of your solutions are prepared. Once ready, we can scan your solutions in about one minute. 11.We will then pool the class data in Table 1 so that each concentration has replicate absorption measurements. Record the absorbance of your unknowns. Add as many columns as needed to record all groups. Pooled class data will be posted on D2L.2
Table 1. Calibration Data.ConcentrationGroup 1AbsorbanceGroup 2 AbsorbanceGroup 3 AbsorbanceGroup 4 AbsorbanceAverageStdevBlank4 ppm6 ppm8 ppm10 ppm15 ppm20 ppm100 ppm Unknown Unknown + 10 ppm SpikeResults and Discussion – 10 points each. 1.Examine the pooled class data and reject outliers using the Grubb’s test.2.Provide an external calibration curve of the linear range, with cleaned up formatting and appropriate error bars. To add error bars, click on your graph and pick Chart Tools – Designon the Excel tool bar (top right). Go to Add Chart Elements drop down menu and select error bars and more error bars options. Choose vertical error bars, both directions and the error amount to be a custom range. Put in the cells thatcontain the standard deviation of your absorbencies into the + and - custom fields. Below is a representative external calibration with y-error bars representing the standard deviation in the pooled class data. Remember, the linear function should beused to describe only the linear portion of the graph. Do not include non-linear data points in your curve. Format the axes and trend line data to the appropriate number of significant figures.

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