Question

Titration is carried out for 3 moles of a mixture of ferrous and ferric sulphate, which required 100 ml of 2 M potassium permanganate in acidic medium. Hence the mole fraction of ferrous sulphate in the mixture is ______ .

(a) 1/3 

(b) 2/3 

(c) 2/5 

(d) 3/5

Answer 1

Correct option: (a) 1/3

Explanation: 

Suppose mole of FeSO₄ = x

Only Fe⁺² undergoes reaction

Fe⁺² + e– → Fe⁺³

Equivalence of FeSO₄ is equal to equivalence of KMnO₄ (i.e., is Oxidising agent) as Fe₂ (SO₄)₃ cannot be oxidized by KMnO₄.

Eq. of FeSO₄ = Eq. of KMnO₄

n_f of FeSO₄ = 1 as it oxidize from + 2 to + 3 oxidation state by KMnO₄

n_f of KMnO₄ in acidic medium = 5.