Answer to Question #208781 in General Chemistry for KPOPOII

Question

A 10.0 mL sample containing Fe³⁺ and Cu²⁺ was diluted to 100.0 mL solution. A 20.0 ml aliquot required 25.0 ml of 0.0500 M EDTA for complete titration. A separate 20.0 ml aliquot of the diluted sample was treated with NH₄F to protect the Fe³⁺. Then the Cu²⁺ was treated with thiourea. Upon addition of 25.0 mL of 0.0500 M EDTA, the Fe³⁺ was liberated from its fluoride complex and formed an EDTA complex. The excess EDTA required 21.5 mL of 0.0180 M Pb²⁺ to reach an end point, using xylenol orange.

Answer 1

The masking agent is thiourea and Auxiliary complexing agent is NH₄F