Question

A solution contains 1.817 mg of CoSO4 (155.0 grams/mole) per mL. Calculate the volume (in mL) of 0.009795 M Zn2 needed to titrate the excess complexing reagent after the addition of 70.00 mL of 0.009005 M EDTA to a 20.00 mL aliquot of the Co2 solution.

Answer 1

85.952 ml
`Zn^2^+` needed to titrate the excess complexing reagent .

Step-by-step explanation:

Lets calculate

After addition of 80 ml of EDTA the solution becomes = 20 + 70 = 90 ml

As the number of moles of
`CoSO_4` =
`(Given mass )/(molar mass)`

=
`(1.817)/(155)`

=0.01172

Molarity =
`(no. of moles)/(volume of solution)`

=
`(0.01172)/(20)`

=0.000586 moles

Excess of EDTA = concentration of EDTA - concentration of CoSO4

= 0.009005 - 0.000586

= 0.008419 M

As M1V1 ( Excess of EDTA ) = M2V2
`(Zn^2^+)`

`0.008419*100ml=0.009795* V2`

`V2=(0.008419*100)/(0.009795)`

V2 =85.952 ml

Therefore , 85.952 ml
`Zn^2^+` needed to titrate the excess complexing reagent .