A solution contains 1.694 mg of CoSO4 (MW 155.0) per mL. Calculate

Question

a) The volume of 0.008640 M EDTA needed to titrate a 25.00 ml aliquot of this solution.

So this is my working out for this section,

Step 1. Moles of CoSO4 = 0.0001694mg * 25mL * (1mol/155g/mol) 2.732*10^-4.

Step 2. Volume of EDTA = 2.732*10-4/ 0.008640 M EDTA = 0.03125 L or 31.25mL.

Now I am just having trouble with section B which is,

b)The volume of 0.009450 M Zn2+ solution needed to titrate the excess reagent after the addition of 50.00 mL of the EDTA solution to a 25.00 mL aliquot of the Co2+ solution.

Answer 1

Calculate mols Co initially.
Calculate mols EDTA in 50 mL of the EDTA solution.
Subtract mols EDTA - mols Co which gives mols excess EDTA.
Then M EDTA = mols/L. Substitute and solve L.