Answer is: 162 g of beryllium.
Chemical reaction: Be + 2H₂O → Be(OH)₂ + H₂.
m(H₂) = 36,0 g.
m(Be) = ?
n(H₂) = m(H₂) ÷ M(H₂)
n(H₂) = 36,0 g ÷ 2 g/mol = 18 mol.
from reaction: n(Be) : n(H₂) = 1 : 1.
n(Be) = n(H₂) = 18 mol.
m(Be) = n(Be) · M(Be).
n(Be) = 18 mol · 9 g/mol = 162 g.
