- NaOH:
\(Na_2O+H_2O\rightarrow2NaOH\)
- Fe(OH)3:
\(Fe_2O_3+3H_2SO_4\rightarrow Fe_2\left(SO_4\right)_3+3H_2O\\ Fe_2\left(SO_4\right)_3+6NaOH\rightarrow2Fe\left(OH\right)_3+3Na_2SO_4\)
- Cu(OH)2:
\(CuO+H_2SO_4\rightarrow CuSO_4+H_2O\\ CuSO_4+2NaOH\rightarrow Cu\left(OH\right)_2+Na_2SO_4\)
Na2O + H2O -> 2NaOH
Fe2O3 + 6KOH -> 2Fe(OH)3 + 3K2O
CuO+ 2NaOH -> Cu(OH)2 +Na2O