146. Solving a chemistry problem

52. Option 2
From a sample of ore of mass m g containing niobium, after appropriate processing, 100.00 ml of the solution were obtained. In measuring cobles with a capacity of 25.00 ml were placed 2.00; 3.00 and 3.00 ml of the resulting solution, and 1.00 ml of standard niobium containing 10.00 μg / ml was added to the third flask. EDTA, tartaric and sulfuric acids, lymagillon IREA were added to each flask, heated to accelerate the complexation reaction, cooled and brought to a mark. The optical densities of the second (Aot. 2) and third (Aot. 3) solutions were measured relative to the solution in the first flask.
Calculate the mass fraction (%) of niobium in the ore for the following options:
Task variant 2
m = 0.1500 g
Aotn.2 = 0.310
Aot.3 = 0.495