58. Solution to Chemistry Problem

7. A 50 ml aliquot of the analyzed solution containing copper (II) was titrated with 0.01 mol/L solution of complexone III (EDTA) in an ammonia buffer medium at a constant external potential E = -0.25 V. Using the data below, plot a titration curve in the coordinates current (i. μA) – volume (V(T), ml) of added titrant and calculate the concentration (mg/L) of copper () in the analyzed solution. (Recommendations for scale: 1 mm cell on graph paper corresponds to V = 0.025 ml on the abscissa axis, and i = 0.25 μA on the ordinate axis.) Based on the nature of the curve, determine which substance is polarographically active at the potential indicated above. Write the equations of the corresponding reaction and give a justified answer. How is the potential selected on the microelectrode for amperometric titration?
Current after adding EDTA solution
0.00 ml 0.50 ml 1.00 ml 1.50 ml 2.00 ml 2.50 ml 3.00 ml
28.0 22.0 16.0 9.50 3.5 0.5 0.5