# need help on these Suppose you obtained the following data from two standard solutions of known...

need help on these Suppose you obtained the following data from two standard solutions of known concentrations using a UV-Vis spectroscope: Analysis # Conc. (mg/L) 8.00 20.00 Absorbance (at 255 nm) 0.160 0.390 What is the concentration (in mg/L) of an unknown solution with an absorbance of 0.200 at 255 nm 10 points)? The unknown solution contains the same analyte as the standard solution does (Assume a path length of 1cm). 10. You prepared a stock solution by dissolving a compound with a molecular mass of 223.00 in a 100 mL volumetric flask. Then you remove a 1.50 mL aliquot and place it in a 250 mL volumetric flask and dilute it to the mark. The absorbance of this diluted solution at 288 nm was 0.502 in a 1.50 cm path length cuvette. The molar absorptivity for this compound at 288 nm is 80000 M'cm'. You should round your answer to three significant figures a. What is the molar concentration of the compound in the 100 ml flask (stock solution) (10 points)? b. How many mg of the compound were used to make the stock solution (10 points)?

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