2. In the determination of copper in steel using flame atomic absorption spectrophotometry, the following table shows the results for the standard copper solutions. Concentration (ppm) 1.0 Absorbance 2.0 3.0 4.0 5.0 6.0 0.118 0.226 0.338 0.422 0.492 0.562 First plot the calibration curve assuming the data are linear. Then plot the residual graph which is the exact deviation of the original data from the data on the line against the concentration of copper. Comment on the results. (20%)

Test Tube Number Cobalt Chloride Concentration    (mol/mL) Absorbance at 510 nm       1 0.000 0.000 2 0.009 0.042 3 0.018 0.92 4 0.027 0.139 5 6 0.036 0.045 0.190 0.236   7   (Unknown)   0.151     1. what is the concentration of unknown cobalt chloride solution? 2. why is the absorbance at the absorption peak ?

You are developing a procedure for determining traces of copper in biological materials using a wet digestion followed by measurements by atomic absorption spectrophotometry. In order to test the validity of the method, you obtain a NIST orchard leaves standard reference material and analyze this material with your procedure five times and obtain a mean of 12.27 ppm with a standard deviation of 0.097 ppm. The NIST sample is listed as 11.7 ppm. Does your method give a statistically valid value at the 95% confidence level?

How much iron ore (that assays at 10.18% Fe) must be used in an analytical procedure that is known to have a low bias of −0.15 g if an overall relative error of 0.48 ppth in the iron content is desired?