Question

The calamine lotion, which is used to relieve skin irritation, is a mixture of Iron Oxides and Zinc. A dry sample of 1.022 g of calamine was dissolved and diluted in acid to 250.0 mL. An aliquot of 10 mL of diluted solution was mixed with Potassium Fluoride to mas the Iron; after adjusting to a suitable pH Zn consume 38.71 mL of EDTA 0.01294 M. A second aliquot of 50.0 mL, buffered properly, was titrated with 2.40 mL of a solution 0.002727 M of ZnY^2- by the following reaction:

Fe ³⁺ (ac) + ZnY ^2- (ac) = FeY^- (ac) + Zn²⁺ (ac)

Calculate the percentages of:

a) ZnO

b) Fe₂O₃ in the sample

Determine the constant conditional formation of complex formation of EDTA with Fe^2- at a pH of:

a) 6.0

b) 4.0

Construct a titration curve for 50.0 mL of Sr2+ 0.0100 M with EDTA 0.0200 M in a buffer solution at a pH of 11.0. Plot the titration curve using the pSr after addition of 0.0 mL; 10.0 mL; 24.0 mL; 25.0 mL; and 30.0 mL of titrant.

Answer 1