A 12.0 gm sample of magnesium is burnt in air to form magnesium oxide ($\mathrm{MgO}$) and magnesium nitrides (${\mathrm{Mg}}_3{\mathrm{N}}_2$). When the products are treated with water, 1. 7 gm gaseous ammonia is generated, What is the mass (in gm) of $\mathrm{Mg}{\left(\mathrm{OH}\right)}_2$formed simultaneously.