Balancing Chemical Equations

• Law of conservation of mass — atoms neither created nor destroyed in chemical reaction.
• Balanced equation — equal number of each atom on both sides.
• Coefficients vs subscripts — only coefficients may be changed when balancing.
• Steps: list elements → count atoms → adjust coefficients → recheck.
• State symbols (s), (l), (g), (aq) in NCERT equations.

1. Unbalanced equation — shows reactants and products but atom counts may differ.
2. Hit-and-trial method — start with complex molecules; balance H and O last often helps.
3. Coefficient — multiplies entire formula; subscript fixed (e.g. H₂O not H₂O₂).
4. Example — Fe + H₂O → Fe₃O₄ + H₂ needs balancing for Fe and O.
5. Combustion — hydrocarbon + O₂ → CO₂ + H₂O (balance C, then H, then O).
6. Physical vs chemical change — melting ice physical; rusting chemical.
7. Skeletal equation — unbalanced; word equation converted to symbols first.
8. NCERT style — always include state symbols where given.
9. Inspection method — no algebra required at Class 10 level.
10. Check — count each element on both sides after balancing.

Balance: Fe + H₂O → Fe₃O₄ + H₂ (high-temperature steam on iron)

Step 1 — Count Fe: L=1, R=3 → put 3 before Fe on left: 3Fe
Step 2 — Count O in Fe₃O₄ = 4 → need 4 H₂O on left
Step 3 — H: left 4×2=8 → need 4 H₂ on right
Step 4 — Balanced: 3Fe + 4H₂O → Fe₃O₄ + 4H₂
Step 5 — Verify Fe:3, O:4, H:8 both sides ✓
Conclusion: balanced equation with coefficients 3, 4, 1, 4.

• Changing subscripts (e.g. H₂O to H₂O₂) — never valid when balancing.
• Forgetting to balance all elements including oxygen last.
• Misconception: coefficients can be fractions in final answer (use integers).
• Ignoring state symbols in NCERT exam answers.
• Balancing only one element and stopping.

• Why must chemical equations be balanced?
• Balance: H₂ + O₂ → H₂O
• What is difference between 2H₂O and H₂O₂?
• Write balanced equation for magnesium burning in air.

Open the Practice tab for graded questions on Balancing Chemical Equations.