[Alfred]

If 4 cm³ potassium manganate(VII) is needed for 25cm³ hydroxyammonium sulphate+25cm³ dilute sulphuric acid.
 How to calculate
a)concentration(mol dm^-3) of ion MnO₄^-
b)concentration of ion Fe²⁺ in solution of hydroxyammonium sulphate with excess iron(III) ammonium sulphate and dilute sulphuric acid
c)mass of ion iron(II) in 1 dm³ of hydroxyammonium sulphate with excess iron(III) ammonium sulphate and dilute sulphuric acid
d)no moles of iron (II) ions required to oxidise 1 mol of hydroxyammonium ion.

Instead of giving Fe³⁺ + 2 NH₃OH⁺  + 2H⁺ + 5e^- --> Fe²⁺ + N₂O + H₂O + 4 H₂
My teacher gives us this one 4 Fe³⁺ + 2 NH₃OH⁺ --> 4 Fe²⁺ + N₂O + H₂O + 6H⁺

[AWK]

You should know at least one concentration  (Fe3+)