9. Solution to Chemistry Problem

1. Calculate the percentage of manganese in steel using the following data obtained under the specified conditions. A 0.2000 g sample of steel was dissolved in nitric acid. Then manganese was oxidized with ammonium persulfate (in the presence of Ag). Phosphoric acid was added to the solution and the solution was diluted to 200.0 cm3. Photometry was carried out by comparison with a standard and zero solution, using the differential method. The standard solution contained 20 mg Mn in 1 dm3. The zero solution was a 0.0050 N solution of KMnO4, with an optical density value equal to 0 with a fully open diaphragm of the FEK-M colorimeter. In relation to the zero solution, Ast = 0.26; Ax = 0.14.