1). A 1.000-mL aliquot of a solution containing Cu2 and Ni2 is treated with 25.00 mL of a 0.04023 M EDTA solution. The solution is then back titrated with 0.02121 M Zn2 solution at a pH of 5. A volume of 18.64 mL of the Zn2 solution was needed to reach the xylenol orange end point. A 2.000-mL aliquot of the Cu2 and Ni2 solution is fed through an ion-exchange column that retains Ni2 . The Cu2 that passed through the column is treated with 25.00 mL 0.04023 M EDTA. This solution required 19.70 mL of 0.02121 M Zn2 for back titration. The Ni2 extracted from the column was treated witn 25.00 mL of 0.04023 M EDTA. How many milliliters of 0.02121 M Zn2 is required for the back titration of the Ni2 solution?

2) A 50.0 mL sample containing Cd2 and Mn2 was treated with 59.1 mL of 0.0400 M EDTA. Titration of the excess unreacted EDTA required 19.3 mL of 0.0140 M Ca2 . The Cd2 was displaced from EDTA by the addition of an excess of CN. Titration of the newly freed EDTA required 10.0 mL of 0.0140 M Ca2 . What were the molarities of Cd2 and Mn2 in the original solution?

3). A 25.0-mL solution of 0.0430 M EDTA was added to a 48.0-mL sample containing an unknown concentration of V3 . All V3 present formed a complex, leaving excess EDTA in solution. This solution was back-titrated with a 0.0440 M Ga3 solution until all the EDTA reacted, requiring 14.0 mL of the Ga3 solution. What was the original concentration of the V3 solution?