Beer's Law

A compound with molecular mass 292.16 g/mol was dissolved in a 5-mL volumetric flask. A 1.00 mL aliquot was withdrawn, placed in a 10 mL volumetric flask, and diluted to the mark. The absorbance at 340 nm was 0.427 in a 1.00 cm cuvette. The molar absorptivity at 340 nm is ε340 = 6130 M–1 cm–1.

A 3.15 x 10-6 M solution of the colored complex exhibited an absorbance of 0.267 at 635 nm in a 1.000 cm cuvet. A blank solution made from distilled water in place of groundwater had an absorbance of 0.019. Find the molar absorptivity of the colored complex. 

A 3.15 x 10-6 M solution of the colored complex exhibited an absorbance of 0.267 at 635 nm in a 1.000 cm cuvet. A blank solution made from distilled water in place of groundwater had an absorbance of 0.019. The absorbance of an unknown solution prepared from ground water was 0.175. Find the concentration of the unknown.