A student is instructed to determine the concentration of a solution of CoCl2 based on absorption of light (spectrometric/colorimetric method). The student is provided with a 0.10 M solution of CoCl2 with which to prepare standard solutions with concentrations of 0.020 M, 0.040 M, 0.060 M and 0.080 M. The student takes the 0.10 M solution and determines the percent transmittance and the absorbance at various wavelengths. The two graphs below represent the data.
a. Identify the optimum wavelength for the analysis. 510 nm (acceptable range 490-520 nm) The student measures the absorbance of 20.0 mL of 0.020 M, 0.040 M, 0.060 M, 0.080 M, and 0.10 M solutions. The data are plotted below.
