Question

A 1.728 g sample of a Pb/Cd alloy was dissolved in acid and diluted to exactly 500 mL. Titration of a 25.00 mL aliquot at a pH = l0 in an NH4 + /NH3 buffer required 43.60 mL of standard 0.01080 M EDTA and involved both cations (Pb2+ and Cd2+). The cadmium ion was then masked by using an HCN/NaCN buffer to bring the pH of a second 25.00 mL aliquot to 10; 32.70 mL of the 0.01080 M EDTA standard was used in this titration and involved only the Pb2+. Calculate the respective percentages of lead and cadmium in the alloy.