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QUESTION
Q56) 3.92 g of ferrous ammonium sulphate crystals are dissolved in 100ml of water. 20ml of this solution requires 18ml of potassium permanganate during titration for complete oxidation. The weight of KMNO4 present in one litre of the solution of ..[ Tamilnadu CET 2002]




SOLUTION

Eq. wt of Ferrous ammonium sulphate=392
Normality of salt solution=(3.92/392)(1000/100)=0.1N
20 ml of 0.1N salt sol.=18ml of KMnO4 sol
Thus from N1V1=N2V2
Normality of KMnO4; N2=(1/9) N
As eq.wt of KMnO4=31.6
∴ strength of KMnO4 sol=(1/9) 31.6=3.5 g/l approxAnswer: (d)