21. Solving a chemistry problem

21. Solving a chemistry problem

39. Calamine, used to reduce skin irritation, is a mixture of zinc and iron oxides. A 1.022 g sample of dried calamine was dissolved in acid and diluted to exactly 250 ml. After the day of iron masking, potassium fluoride was added to 10.0 ml of the diluted solution, and after establishing an appropriate pH, Zn2 was titrated using 38.7 or 0.0129 M EDTA solution. In the second portion of the solution with a volume of 50.0 ml, the desired pH value was set and it was titrated, using 2.40 ml of a 0.00272M ZnY2- solution. Reaction: Fe3 ZnY2- = FeY- Zn2. Calculate the percentage of ZnO and Fe2O3 in the sample.

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