The decomposition of 19.6 g of a divalent metal hydroxide resulted in 16 g of this metal oxide. Identify the metal.

General reaction equation:

M (OH) 2 (t) = MO + H2O, where M is an unknown metal.

The amount of substance M (OH) 2:

v (M (OH) 2) = m (M (OH) 2) / M (M (OH) 2) = 19.6 / (M (M) + 34).

Amount of substance MO:

v (MO) = m (MO) / M (MO) = 16 / (M (M) + 16).

According to the reaction equation, 1 mol of MO is formed from 1 mol of M (OH) 2, therefore:

v (M (OH) 2) = v (MO),

19.6 / (M (M) + 34) = 16 / (M (M) + 16),

whence M (M) = 64 (amu), which corresponds to copper (Cu).