A student prepares five aqueous CuSO4 standard solutions by dilution from a 0.500 M stock and measures their absorbance at 635 nm in a 1.00 cm cuvette. The blank is distilled water. Concentrations and absorbances are: 0.050 M (A=0.105), 0.100 M (A=0.210), 0.200 M (A=0.420), 0.300 M (A=0.630), 0.400 M (A=0.840). An unknown CuSO4 solution gives A=0.525 in the same cuvette.
What is the molar absorptivity (epsilon) of CuSO4 at 635 nm?
- Acheck_circle
2.10 M^-1 cm^-1
- B
21.0 M^-1 cm^-1
- C
0.477 M^-1 cm^-1
- D
0.210 M^-1 cm^-1
Explanation
Beer-Lambert: A = epsilon * b * c. With b=1.00 cm, slope of A vs c equals epsilon = 2.10 M^-1 cm^-1.