Question

The following information is to be used for the next two questions. Molar absorptivity data for the cobalt and nickel complexes with 2,3-quinoxalinedithiol are ε_Co = 36400 and ε_Ni = 5520 at 510 nm and ε_Co = 1240 and ε _Ni = 17500 at 656 nm. A 0.475-g sample was dissolved and diluted to 100.0 mL. A 25.0-mL aliquot was treated to eliminate interferences; after addition of 2,3-quinoxalinedithiol, the volume was adjusted to 50.0 mL. This solution had an absorbance of 0.963 at 510 nm and 0.292 at 656 nm in a 1.00-cm cell.

Calculate the concentration of cobalt (in ppm) in the initial solution prepared by dissolving the sample.

Calculate the concentration of nickel (in ppm) in the initial solution prepared by dissolving the sample.