Spectrum of a Mixture. The W-visible spectra of pure solutions of cobalt2+, nickel2′ and copper2+ salts, and of a mixture of the three, are given on the CD-ROM over the wavelength range 350-820 nm. Instead of using absorbance readings at only three wavelengths to calculate the concentrations of the three salts in the mixture, use the data at all 236 wavelength data points to calculate the three concentrations. Use the relationship A = E~C, where E, the molar absorptivity, is a dimensionless constant for a particular species at a particular wavelength, b is the light path length (1 .OO cm in this experiment) and c is the molar concentration. For the mixture, Aobsd = E~~C~~ + EN~CN~ + E~~C~~ at each wavelength. Use the Solver Statistics macro to obtain the standard deviations of the three concentrations.
