When 1.187 g of a metallic oxide is reduced with excess hydrogen 1.054 g of the metal is produced. what is the metallic oxide?

Mass O = 1.187 - 1.054 = 0.133 g

Moles O = 0.133 g / 16 g/mol = 0.00831

Moles metal = 2 x 0.00831 = 0.0166

Atomic mass metal = 1.054 g / 0.0166 = 63.4 g/mol

(this is the atomic mass of Cu)

so the metal oxide is Cu2O