Question

A sample of Ferrous sulphide reacts with dil. H₂SO₄ to from H₂S which contains 9% hydrogen by volume. The percentage of fee in the sample, is ______.

Options

• 5.92

• 6.05

• 7.06

• 0.25

Answer 1

A sample of Ferrous sulphide reacts with dil. H₂SO₄ to from H₂S which contains 9% hydrogen by volume. The percentage of fee in the sample, is 5.92.

Explanation:

Since the sample of FeS contains some free metal Fe, hence H₂ is liberated.

FeS + H₂SO₄ = FeSO₄ + H₂S 22.4 ℓ at N.T.P

Fe +  H₂SO₄ = FeSO₄ + H₂  22.4 ℓ at N.T.P

The liberated H₂S contains 9% by volume of H₂ hence rest 91% H₂S

Now 22.4 ℓ of H₂S at N.T.P are obtained from 88 g of H₂S

∴ 91 ℓ of H₂S at N.T.P are obtained from `(88 xx 91)/22.4` = 357.5 g of FeS

∴ For 9 ℓ of H₂ required Fe = `(56 xx 9)/22.4` g = 22.5 g of Fe

∴ The percentage of Fe in the sample of FeS `(22.5 xx 100)/(357.5 + 22.5)` = 5.92