Problem- A spectrophotometer was calibrated with a 6.840 10-4 M (in Cu) Cu-neocuproine solution. This calibration was carried out in a 1.00 cm cell, and yielded an absorbance of 0.2850 AU. An unknown was then analyzed in this same spectrophotometer, but using a 2.50 cm cell. If the absorbance of the unknown was 0.2270 AU, what is the Cu concentration?
Solve the above problem and provide steps with explanation