Copper(i) oxide, cu2o, is reduced to metallic copper by heating in a stream of hydrogen gas. what mass of water is produced when 10.00 g copper is formed?

Answer is: mass of water is 1.41 g.
Balanced chemical reaction: Cu₂O + H₂ → 2Cu + H₂O.
m(Cu) = 10.00 g.
n(Cu) = m(Cu) ÷ M(Cu).
n(Cu) = 10 g ÷ 63.55 g/mol.
n(Cu) = 0.157 mol.
From chemical reaction: n(Cu) : n(H₂O) = 2 : 1.
n(H₂O) = 0.079 mol.
m(H₂O) = n(H₂O) · M(H₂O).
m(H₂O) = 0.079 mol · 18 g/mol.
m(H₂O) = 1.41 g.