137. Задачка по химии №013 705

To construct a calibration graph for the determination of manganese, the volumes of a standard manganese solution (C-1.25 mg / ml) indicated below were introduced into volumetric flasks of 250.0 cm3 and manganese was oxidized to permanganate ion. Optical density was measured relative to a solution prepared from 10.0 cm3 of a standard solution and the following values ​​were obtained:
V, cm3 10.0 11.0 12.0 13.0 14.0 15.0
A 0.00 0.20 0.40 0.60 0.80 1.01
A sample of ore weighing 0.5000 g was dissolved and after oxidation of manganese to the permanganate ion, the solution was diluted with water to 250.0 cm3. The optical density for the resulting colored solution under the same conditions was 0.320. Determine the content (%) of manganese in the ore.