6. Solution to Chemistry Problem

10. Aniline was distilled off from 250.0 ml of waste water with water vapor and the distillate was evaporated to dryness in the presence of acid, the residue was dissolved in V ml of a buffer solution with pH 3.5, Val ml of the resulting solution were extracted with 4.0 ml of chloroform in the presence of bromocresol purple and the optical density of the organic layer Ax was measured. A standard solution containing 0.30 g/l of aniline was used to plot the calibration graph. To do this, 10.0 ml of it was diluted to 500.0 ml with water, four samples of Vst ml were taken, each was evaporated to dryness, the residue was dissolved in 20.0 ml of the same buffer solution, 2.0 ml of the resulting solution was extracted and Ast was measured similarly to the studied samples:
Vst, ml 5.0 10.0 15.0 20.0
Ast 0.080 0.165 0.245 0.325
Calculate the concentration of aniline (μg / l) in wastewater using the following data:
Option 1 2 3

V, ml 5.0 10.0 15.0
Val, ml 2.0 5.0 5.0
Ax 0.130 0.195 0.310
Solution for option 1