68. 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 an 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 Cu2 copper cation in the analyzed solution (do not take into account the dilution of the solution during the titration process).
Option 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
g 0.0813 0.100 0.150 0.199 0.220 0.222 0.222 0.222
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 the abscissa axis V (EDTA) = 0.05 ml, and along the ordinate axis - A = 0.005.

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