(Solution) - A 1 000 mL sample of unknown containing Co2 and Ni2 was -(2025 Original AI-Free Solution)

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A 1.000-mL sample of unknown containing Co2+ and Ni2+ was treated with 25.00 mL of 0.03872 M EDTA. Back titration with 0.02127 M Zn2+ 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 CO2+ more than Ni2+. The Ni2+ that passed through the column was treated with 25.00 mL of 0.03872 M EDTA and required 25.63 mL of 0.02127 M Zn2+ for back titration. The CO2+ 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?