1) Chemists suspected that an impure copper lump contained a signifi cant amount of cobalt. Cobalt would be
oxidised to Co2+ ions that would remain in the electrolyte solution. The spectrogram below gives the results
of analysis of the solution. The two ions absorb at distinctly different wavelengths.
a) i)Which analytical technique was used to perform this analysis?
A calibration graph was constructed using Co2+(aq) solutions of known concentrations.
ii. What wavelength would you select to construct this curve?
Solution
b) A Co2+(aq) solution of unknown concentration registered an absorbance reading of 0.350. Determine the concentration of Co2+ ions in this solution.
Solution