
Tesfaye D. answered 12/04/18
PhD in Chemistry with Research and Teaching Experiences
The reaction that corresponds to your question:
Zn + 2HCl ---------- ZnCl2 + H2
mole to mole: 1 mol 2 mol 1 mol 1mol
Thus 1 mol of H2 is produced from 1 mol Zn
1 mol H2 / 1mol Zn = 2 g H2/ 65.38 g Zn (use the molar mass of H2 and Zn)
If you start with 31.9 g Zn, then
(2 g H2/65.38 g Zn ) x 31.9 g Zn = 0.98 g H2 will be produced.