22. Solving a chemistry problem

23(1). When condensed with aniline, furfural C4H3OCHO forms a red compound C4H3OCH(C6H4NH2)2. The molar light absorption coefficient of which at 518 nm is equal to ε’518 = 6.20*104.
Furfural and its derivatives form yellow compounds when condensed with benzidine. At 413 nm, the molar light absorption coefficients of the condensation products are equal: ε´413 = 2.00 * 102 (for furfural), ε2413 = 1.00 * 103 (for methylfurfural and other derivatives).
V ml of wastewater from plastics production was taken for analysis, furfural and its derivatives were distilled into a 500.0 ml flask and brought to the mark with water. The prepared reagent mixture containing aniline was added to a 5.00 mL aliquot and diluted with water to 20.00 mL. The optical density of A518 was measured at 518 nm and a cuvette l = 1.0 cm. A benzidine hydrochloric acid solution was added to another 50.00 ml aliquot and diluted to 100.0 ml. We measured the optical density of A413 at 413 nm and a cuvette l = 5.0 cm
Calculate the concentration (mg/l) of furfural (M(C4H3OCHO) = 96.0854 g/mol) and its derivatives based on methylfurfural (M(C5H5OCHO) = 110.1158 g/mol) in wastewater for the following options:


Option Wastewater sample volume V, ml A518 A413
1 100 0.525 0.450