21. Solving a chemistry problem

181. When determining chromium by the method of additions, a sample of the product a = 0.4600 g was dissolved, the volume of the solution was brought to 50 ml. Then 20 ml aliquots of the solution were withdrawn into two 50 ml volumetric flasks. A standard solution of chromium was added to one of them, after which its concentration became equal to Сst = 4.18 10–4 mol/l. Hydrogen peroxide was added to both flasks and the volumes were adjusted to the mark, photometered and obtained Ax = 0.20 and Ax st = 0.42. Calculate the percentage of chromium in the product.