Find how many L of hydrogen gas are formed at STP if 30 g of Zn reacts with hydrogen.
The information you have provided is incorrect. When zinc reacts with hydrogen, hydrogen is not produced. Hydrogen is already there, it cannot be produced during the reaction.
Instead the reaction may lead to the formation of zinc hydride or ZnH2.
Though this is not the usual way in which ZnH2 is produced. Reactions such as
2LiH + ZnBr2 → ZnH2 + 2LiBr
2NaH + ZnI2 → ZnH2 + 2NaI
among many others are more widely used to produce zinc hydride.
If this is not what you require, you would have to present the question in a more accurate way for a proper answer.
We'll write the reaction first:
Zn + 2H+ -> Zn2+ + H2
Since the moles of Zn are equal to the moles of H2, we'll have to determine the moles of Zn.
Moles of Zn = mass/molar mass
Moles of Zn = 30/65.41
Moles of Zn = 0.4586 mol
Therefore, the moles of H2 = 0.4586 mol
We also know that 1 mol of gas at standard temperature and pressure has a volume of 22.4L.
The volume of H2 = 0.4586 * 22.4 = 10.27 L
The volume of hydrogen gas formed when 30g Zn reacts is of 10.27 L.