A vessel fitted with a weightless, frictionless piston of 0.246 m 2 area of cross section contains excess concentrated HCl. The piston moved 0.1 m outward when 0.075 kg of iron fillings were added at

Question

A vessel fitted with a weightless, frictionless piston of $0.246 m^{2}$ area of cross section contains excess concentrated HCl. The piston moved 0.1 m outward when 0.075 kg of iron fillings were added at 300 K and 1 atm pressure. The solution left behind was found to contain iron as Fe(II) only. The approximate percentage purity of the iron sample is y. (Assume gas/gases behaves/behave ideally and impurity does not react with conc. HCl ). Then, $\frac{y}{15}$ is

(R = 0.082 L-atm/K-mol, Fe = 56)

TestHub · Accepted Answer

Piston displacement gives gas volume: V = A × h = 0.246 × 0.1 = 0.0246 m 3 = 24.6 L n ( H 2 ​ ) = RT P V ​ = 0.082 × 300 1 × 24.6 ​ = 1 m o l F e + 2 H Cl → F e C l 2 ​ + H 2 ​ Hence, 1 mol H₂ requires 1 mol Fe = 56 g. % p u r i t y = 75 56 ​ × 100 ≈ 74.7% ≈ 75% 15 y ​ = 15 75 ​ = 5

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