Question

At STP, a certain amount of hydrogen is produced by the reaction of 550 g of impure zinc with excess amount of HCl. The same volume of hydrogen at STP reduces `Fe_(3)O_(4)` and produces 336 g of iron. Find the percentage of zinc. (Atomic mass of Zn is 65)

Answer 1

`Zn+2HCl to ZnCl_(2) + H_(2) , 4H_(2) + Fe_(3)O_(4) to 4H_(2)O + 3Fe`
Amount of iron produced ` = 336 g rArr` number of moles of iron ` = (336)/56 = 6`
To produce 6 moles of iron, it requires 8 moles of hydrogen which further requires 8 moles of Zn.
Weight of Zn = `8 xx 65.5 = 524` g, % purity =`(524)/(550) xx 100 = 95.27 %`.