Question

If 78.4 grams of aluminum metal react with excess hydrochloric acid, how many grams of hydrogen gas can be produced?2al + 6hcl yields 2alcl3 + 3h2

Answer 1

Answer is: 8,7g.
Chemical reaction: 2Al + 6HCl → 2AlCl₃ + 3H₂.
m(Al) = 78,4g.
n(Al) = m(Al)÷M(Al) = 78,4g ÷ 27g/mol = 2,9 mol.
n - amount of substance.
from reaction: n(Al) : n(H₂) = 2 : 3.
2,9mol : n(H₂) = 2 : 3.
n(H₂) = 4,35 mol.
m(H₂) = n(H₂)·M(H₂) = 4,35mol · 2g/mol = 8,7g.