A quantity of 5.56 g of FeS O 4 ⋅ x H 2 O was dissolved in water to make 250 ml of solution. Twenty five millilitres of this solution requires 20 ml of 0.02 M KMn O 4 in acidic medium. The value

Question

A quantity of 5.56 g of FeS O 4 ​ ⋅ x H 2 ​ O was dissolved in water to make 250 ml of solution. Twenty five millilitres of this solution requires 20 ml of 0.02 M KMn O 4 ​ in acidic medium. The value of 'x' is

TestHub · Accepted Answer

mmol KMn O 4 ​ = 20 x 0.02 = 0.4; F e 2 + in 25 ml = 5 x 0.4 = 2 mmol, so 20 mmol in 250 ml. Molar mass = 5.56/0.02 = 278. FeS O 4 ​ = 152, so 18x = 126, x = 7, option (d).

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