111. Solving a chemistry problem

The determination of iron (II) was carried out by a photoelectrocolorimetric method based on the reaction of formation in aqueous solutions at pH 4-6 of an orange-red complex of iron (II) with 1,10-phenanthroline. In two volumetric flasks with a capacity of 25 ml each, the test and reference solutions containing the iron (II) complex with 1,10-phenanthroline were prepared. To do this, an aliquot of the analyzed solution with an unknown concentration Cx of iron(II) was placed in one flask with a volume of 10 ml, and 4 ml of a standard solution with 1 mg/ml of iron(II) was placed in another flask, the necessary reagents were added to both flasks to carry out the photometric reaction and dilute the volume of the solutions to the mark with water. The optical density Ax=320 and Ast=0.315, respectively, of the test and reference solutions was measured on a photoelectrocolorimeter at 508 nm, in a cuvette with an absorbing layer thickness of 1.00 cm. iron(II). Calculate the content (mg) of iron(II) in 100 ml of the analyzed solution.