Chemistry - Ideal Gas Question with Solution | TestHub

A vessel fitted with a weightless, frictionless piston of $0.246{\mathrm{m}}^2$ 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. If % purity of iron in iron fillings is $\mathrm{y}\%$ then find nearest integer value of $\left(\frac{\mathrm{y}}{15}\right)$ ?

(Assume gas/gases behaves/behave ideally and impurity does not react with conc. HCl and initial volume is negligible ). 

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