137. Solving a chemistry problem

137. Solving a chemistry problem

To determine the content of copper (2+) in the presence of iron (3+), copper was preliminarily separated on a cation exchanger in the H + form. 5.00 ml of the test solution was added to the chromatographic column. To extract copper, the column was washed with a 0.5 M hydrochloric acid solution and the solution was placed in a volumetric flask with a capacity of 250.0 ml. Took 25.00 ml of the resulting solution and introduced into a volumetric flask with a capacity of 50.0 ml, added 15 ml of 25% ammonia solution, brought up to the mark with water and measured the optical density - Ax = 0.36. To build a calibration graph, V ml of a copper sulfate solution (T (Cu) = 1 * 10-3) was placed in 4 volumetric flasks with a capacity of 50.0 ml, 15 ml of a 25% ammonia solution was added, brought up to the mark with water and measured the optical density of the obtained solutions:
V, ml 2.0 5.0 10.0 15.0
A 0.05 0.15 0.30 0.45
Determine the concentration (mg / ml) of copper in the analyzed solution.