Exercise on Balancing Chemical Reactions

Balance the following chemical reactions:

• Mg (s) + H₂O (l) → Mg(OH)₂ (aq) + H₂ (g) where aq means dissolved in water
• CO (s) + O₂ (g) → CO₂O₃ (s)
• C₂H₄ (g) + O₂ (g) → CO₂ (g) + H₂O (g)
• Fe (s) + HCl (aq) → FeCl₃ (aq) + H₂ (g)