Pure hexane has a negligible ultraviolet absorbance above a wavelength of 256 nm. A solution prepared by dissolving 25.8 mg of benzene (MM 78.11) in hexane and diluting to 250.0 mL had an absorption peak at 256 nm and absorbance of 0.266 in a 1.000-cm cell. a) Find the molar absorptivity of benzene at this wavelength.
b) A sample of hexane contaminated with benzene has an absorbance of 0.070 at 256 nm in a cuvet with a 5.000-cm path length. Find the concentration of benzene in mg/L.