Question

A cream to treat skin problems contains a mixture of zinc and iron oxides. A portion of 1.022 g is dissolved in acid and the volume is made up to 250.0 mL. One 10.00-mL aliquot of the solution is treated with an excess of K_F to mask Fe. Zn²⁺ is then titrated in an alkaline buffer by 38.78 mL of 0.0129 M EDTA. After, a second 50.00 mL aliquot of the initial solution is titrated by 2.40 mL of a 0.00273 M ZnY^2- solution to measure iron. Determine the percentage of ZnO and Fe₂O₃ in the cream.

Answer 1