Question

How do you form an equation for such problems?
Q.54. When potassium permanganate is titrated against ferrous ammonium sulphate, the equivalent weight of ferrous ammonium sulphate is:
(a) M
(b) M / 2
(c) M / 5
(d) M / 3

Answer 1

Dear student,
the formula of FAS is (NH₄)₂SO₄ . FeSO₄ . 6 H₂O ; out of this formula the ion of iron will take part in reaction with pot. per magnate therfore the rest of ions are called as spectators ions ; while writting the redox reactions we genrally use only those ions or molecules which are necessary ; so the ionic reaction is given as ;
MnO₄^- + 5Fe²⁺ +8 H⁺ $\to$ Mn²⁺ +5 Fe³⁺ +4 H₂O
again ; for determining the eq. wt of oxidising or reducing agent ; then eq.wt .= mol.mass / total change in oxidation no.
in the above reaction eq. wt FAS = M / 5
Regards