A 1.000-mL sample of unknown containing Co 2+ and Ni 2+ was treated with 25.00mL of 0.03872M EDTA. Back titration with 0.02127 M Zn 2+ at pH 5 required 23.54 mL to reach the xylenol orange end point. A 2.000-mL sample of unknown was passed through an ion exchange column that retards Co 2+ more than Ni 2+. The Ni 2+ that passed through the column was treated with 25.00 mL of 0.03872M EDTA and required 25.63 mL of 0.02127 M Zn 2+ for back titration. The Co 2+ emerged from the column later. It, too, was treated with 25.00 mL of 0.03872 M EDTA. How many milliliters of 0.02127 M Zn2+ will be required for back titration?