Question

A sample weighing 1.25 mg containing a certain compound M (FW 292.16 g/mol) was dissolved in
solvent in a 5.00 mL volumetric flask. A 1.00 mL aliquot was drawn up, placed in a 10.00 mL volumetric and
diluted to the mark with solvent. The absorbance of this solution at 340 nm was 0.427 in a 1.00 cm
cuvette. The molar absorptivity at 340 nm for the compound is 6130 M]1 cm]1.
(a) Calculate the concentration of compound M in the 5 mL volumetric flask.
(b) Calculate the percent purity of the compound.

Answer 1

Absorbance = ecl
0.427 = 6130*c*1
Solve for c in mols/L. This the concentration in the 10.00 mL cuvette. The concentration in mols/L in the 5.00 cuvette is 10x that

grams is c in mols/L x molar mass = ? and that is the concn in g/L. You had 5 mL cuvette; therefore, grams in the 5.00 cuvette will be ?grams in 1L x (5/1000) = ? and that is answer for A (in grams). I would change that to mg. .
B. is [(ans for A in mg/1.25)]*100 = ? I'm guessing about 80% purity.









absorbance = ec