Titrating with EDTA? (I give points for Best Answer)?

A solution contains 1.694mg of CoSO4 (155g/mol) per mL. Calculate the volume of 0.0864 M EDTA needed to titrate a 25 mL aliquot of this solution.

Also, calculate the volume of 0.009450 M Zn2+ needed to titrate the excess reagent after addition of 50mL of 0.008640 M EDTA to a 25 mL aliquot of this solution.

Very confused here and just needed help figuring it out for future problems. Any help is appreciated :-).

Answer:
The reaction is
Co2+ + H4Y >> CoH2Y + 2H+
1.694 mg = 0.001694 g
0.001694 g / 155 = 0.0000109 moles in 1 mL
0.0000109 x 25 = 0.000273 moles in 25 mL
V = moles / M = 0.000273 / 0.0864 = 0.00316 L = 3.16 mL EDTA needed for the reaction

Now I don't know the concentration of EDTA because in the first question you said 0.0864 and in the second you said 0.00864.
In any case moles EDTA = Molarity x 0.050 L
Moles EDTA in 50 ml - moles EDTA in 25 mL = moles EDTA in excess = moles Zn2+ needed for the reaction
V = moles / 0.009450
I hope this can help you
If you can't figure this out yourself how can you possibly decide which answer is best?

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