the theoretical yield of hydrogen gas is 10 g
calculation
Step 1: write the equation for reaction
Zn + 2 HCl → zncl₂ + H₂
Step 2: use the mole ratio to find the moles of H₂
from equation above Zn : H₂ is 1: 1 therefore the moles of H₂ = 5.00 moles
Step 3: find the theoretical yield(mass) for H₂
mass = moles × molar mass
from periodic table the molar mass of H₂= 1×2 = 2 g/mol
mass = 5 moles × 2 g/mol = 10 grams