- $Na_2S+2HCl\to 2NaCl+H_2S$
$S^{2-}+ 2H^+ \to H_2S$
- $Ba(NO_3)_2+K_2SO_4\to BaSO_4+2KNO_3$
$Ba^{2+}+ SO_4^{2-}\to BaSO_4$
- $NaOH+HCl\to NaCl+H_2O$
$H^+ + OH^-\to H_2O$
- $CaCl_2+Na_2CO_3\to CaCO_3+2NaCl$
$Ca^{2+}+ CO_3^{2-}\to CaCO_3$
- $Na_2SO_3+2HCl\to 2NaCl+SO_2+H_2O$
$SO_3^{2-}+2H^+\to SO_2+H_2O$
- $Cu(NO_3)_2+2KOH\to Cu(OH)_2+2KNO_3$
$Cu^{2+}+ 2OH^-\to Cu(OH)_2$