3. An aliquot of the analyzed solution containing copper (II), with a volume of 50 ml, was titrated with a 0.01 mol/l solution of complexone III (EDTA) in an ammonia buffer medium at a constant external potential E = -0.25 V.
According to the data below, build a titration curve in the coordinates current (i. μA) - volume (V (T), ml) of the added titrant and calculate the concentration (mg / l) of copper () in the analyzed solution. (Recommendations for the scale scale: 1 mm cell on millimeter paper corresponds to the abscissa axis V = 0.025 ml, and along the ordinate axis i = 0.25 μA.) Based on the nature of the curve, determine which substance at the above potential is polarographically active. Write the equations for the corresponding reaction and give a reasonable answer. How is the potential selected on the microelectrode for amperometric titration.
Current after addition of EDTA solution
0.00 ml 0.50 ml 1.00 ml 1.50 ml 2.00 ml 2.50 ml 3.00 ml
19.9 14.0 7.75 1.75 0.50 0.50 0.50

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