The theoretical yield of H₂ in grams is =
calculation
Zn(s) + 2HCl(aq) → ZnCl₂(aq) +H₂
Step 1: find the moles Zn
moles = mass÷ molar mass
from periodic table the molar mass of Zn = 65.4 g/mol
moles is therefore = 25.3 g/65.4 g/mol=0.387 moles
Step 2: use the mole ratio to determine the moles of H₂
from given equation Zn:H₂ = 1:1 therefore the moles of H₂ is also =0.387 moles
Step 3: find theoretical mass of H₂
mass= moles× molar mass
from periodic table the molar mass of H₂ = 1 × 2 = 2 g/mol
mass =0.387 moles × 2 g/mol =0.774 grams
