Abstract: This study was designed to investigate the relationship between the concentration of aqueous copper (II) sulfate (CuSO4) solutions and their light absorbance, and to validate the Beer-Lambert Law for quantitative analysis. A series of standard solutions, with concentrations from 0.0131 M to 0.510 M, were prepared by serially diluting a stock solution. We measured the absorbance of each solution at a wavelength of 640 nm with a UV-visible spectrophotometer. The resulting data showed a strong linear relationship (y=2.2344x−0.0084, with an R2 value of 0.9996). Using this calibration, we determined the concentration of an unknown CuSO4 solution to be 0.453 M, differing from its theoretical concentration by a minimal error of just 0.658%. These results confirm that the Beer-Lambert Law is both applicable and accurate for this chemical system in the tested range.