126. Solving a chemistry problem

68a. An aliquot of the analyzed solution containing the copper cation Cu2, 50.00 ml in volume, was titrated with a standard solution of complexone III (EDTA) in the presence of acetate buffer. The end of the titration was determined using the method of spectrophotometric titration at a wavelength of 745 nm, at which only the reaction product—copper(II) complexonate—absorbs light.
Using the data below, construct a titration curve1 in the coordinates optical density A - volume V (EDTA) of the added titrant and calculate the molar concentration and titer (g/ml) of the copper cation Cu2 in the analyzed solution (do not take into account the dilution of the solution during the titration process).
Option A
c(EDTA), mol/l
Optical density of solution A
after addition of EDTA
1.00 ml 1.50 ml 2.00 ml 2.50 ml 3.00 ml 3.50 ml 4.00 ml
0.1000 0.122 0.183 0.245 0.305 0.335 0.338 0.338
To construct a titration curve when applying scale scales to the coordinate axes, it is recommended to choose for each scale such a scale at which one small cell on millimeter paper would correspond to V(EDTA) = 0.05 ml along the abscissa axis, and A = 0.005 along the ordinate axis.