Calculate the relative atomic mass of a divalent metal if 18 g of its hydroxide forms 14.4 g

Calculate the relative atomic mass of a divalent metal if 18 g of its hydroxide forms 14.4 g of a metal oxide during decomposition.

Let M be an unknown divalent metal, MO is its oxide, and M (OH) 2 is its hydroxide.

Let’s write the reaction equation:

M (OH) 2 (t) = MO + H2O

Let’s find the amount of substance M (OH) 2:

v (M (OH) 2) = m (M (OH) 2) / M (M (OH) 2) = 18 / (M (M) + (16 + 1) * 2) = 18 / (M (M ) + 34) (mol).

Let’s find the amount of substance MO:

v (MO) = m (MO) / M (MO) = 14.4 / (M (M) + 16) (mol).

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),

18 / (M (M) + 34) = 14.4 / (M (M) + 16),

M (M) = 56 (g / mol) = 56 (amu), which corresponds to the metal iron (Fe).

Answer: 56 amu