The density of a 3 M Sodium thiosulphate solution (Na₂S₂O₃) is 1.25 g per ml. Calculate

(i) the percentage by weight of sodium thiosulphate,

(ii) the mole fraction of sodium thiosulphate and

(iii) the molalities of Na⁺ and $$S_2O_3^{-2}$$ ions

Hydroxylamine reduces iron (III) according to the equation:

2NH₂OH + 4Fe³⁺ $$\to$$ N₂O(g) $$ \uparrow $$ + H₂O + 4Fe²⁺ + 4H⁺

Iron (II) thus produced is estimated by titration with a standard permanganate solution. The reaction is :

$$MnO_4^-$$ + 5Fe²⁺ + 8H⁺ $$\to$$ Mn²⁺ + 5Fe³⁺ + 4H₂O

A 10 ml sample of hydroxylamine solution was Diluted to 1 litre. 50 ml of this diluted solution was boiled with an excess of iron (III) solution. The resulting solution required 12 ml of 0.02 M KMnO₄ solution for complete oxidation of iron (II). Calculate the weight of hydroxylamine in one litre of the original solution. (H = 1, N = 14, O = 16, K =39, Mn = 55, Fe = 56)

A 1.00 gm sample of H₂O₂ solution containing X percent H₂O₂ by weight requires X ml of a KMnO₄ solution for complete oxidation under acidic conditions. Calculate the normality of the KMnO₄ solution.

(i). A sample of MnSO₄.4H₂O is strongly heated in air. The residue is Mn₃O₄.

(ii). The residue is dissolved in 100 ml of 0.1N FeSO₄ containing dilute H₂SO₄.

(iii). The solution reacts completely with 50 ml of KMnO₄ solution.

(iv). 25 ml of the KMnO₄ solution used in step (iii) requires 30 ml of 0.1 N FeSO₄ solution for complete reaction.

Find the amount of MnSO₄.4H₂O present in the sample.