Have been struggling with this, any help is appreciated :
Calculate the masses of anhydrous Iron(II) and Iron(III) sulphate present in 1dm3 Of solution from the following results:
25cm3 of the solution was oxidised by 23.0cm3 of 0.02mol dm-3 KMnO4
After reduction by zinc and dilute sulphuric acid, 25.00cm3 of the solution required 40.0cm3 of the same KMnO4 solution.
(Fe = 55.8, S=32.1, O=16.0)
(Use MnO4^- + 8H+ 5e- -> Mn^2+ 4H2O)