\[ 3NaOH + FeCl_3 → Fe(OH)_3 ↓ + 3NaCl \]
\[ 3Na^+ + 3OH^- + Fe^{3+} + 3Cl^- → Fe(OH)_3 ↓ + 3Na^+ + 3Cl^- \]
\[ Fe^{3+} + 3OH^- → Fe(OH)_3 ↓ \]
\[ Al(OH)_3 + 3HCl → AlCl_3 + 3H_2O \]
\[ Al(OH)_3 + 3H^+ + 3Cl^- → Al^{3+} + 3Cl^- + 3H_2O \]
\[ Al(OH)_3 + 3H^+ → Al^{3+} + 3H_2O \]
\[ Na_2SO_3 + H_2SO_4 → Na_2SO_4 + SO_2 ↑ + H_2O \]
\[ 2Na^+ + SO_3^{2-} + 2H^+ + SO_4^{2-} → 2Na^+ + SO_4^{2-} + SO_2 ↑ + H_2O \]
\[ SO_3^{2-} + 2H^+ → SO_2 ↑ + H_2O \]