Question

When 15.0 g of zinc metal reacts with excess hcl, how many liters of h2 gas are produced at stp?

Answer 1

M(Zn)=65.4 g/mol
15.0g Zn*1mol Zn/65.4 g Zn = 15/65.4 mol Zn

                               Zn +2HCl--->ZnCl2 + H2
by equation          1 mol                            1 mol
from the problem 15/65.4 mol                15/65.4 mol

Molar volume of any gas under STP = 22.4 L/mol

 15/65.4 mol H2 * 22.4 L/1 mol= 5.14 L H2