Question

1. A sample weighing 1.30 mg was analyzed to determine the concentration of a certain compound (FW =292.16 g/mol) using UV/Visible spectrometry. First, the sample was dissolved in 5.00 mL volumetric flask. A 1.00 mL aliquot was drawn up, placed in a 10.0 mL volumetric flask and diluted to the mark with DI water. The absorbance of this solution was measured at 530 nm and it gave an absorbance of 0.427 in a 1.00 cm cuvette. According to the Beer’s law, the molar absorptivity at 514 nm for this compound is 6130 Lmol-1cm-1. Find the concentration of this compound in the 5.00 mL volumetric flask. Calculate the mass percent of this compound in the sample.
I really don't know how to do it, please help!!

Answer 1

A = ebc
0.427 = 6130*1*c
c in the 10 mL flask = ? M. c in c in 5.00 mL flask = 10x that = ?
mols 5.00 flask = M x L
g 5.00 flask = mols x molar mass = ?
mass% in sample = (g in 5.00 flask/mass sample)*100 =?
mass% =