Neutralisation

• Neutralisation — acid + base → salt + water + heat (often).
• H⁺ + OH⁻ → H₂O — core ionic idea.
• Applications: antacids, treating bee stings, soil treatment, factory effluent.
• Strong acid + strong base → neutral salt; pH ≈ 7.
• Exothermic nature of neutralisation.

1. General equation — Acid + Base → Salt + Water.
2. Example — HCl + NaOH → NaCl + H₂O.
3. Antacid — Mg(OH)₂ or NaHCO₃ neutralises excess HCl in stomach.
4. Heat released — exothermic; temperature rises in lab mixing.
5. Ionic equation — H⁺(aq) + OH⁻(aq) → H₂O(l).
6. Soil treatment — lime (CaO/Ca(OH)₂) neutralises acidic soil.
7. Factory waste — neutralise before discharge to prevent environmental damage.
8. Bee sting — acidic → baking soda (mild base) helps.
9. Wasp sting — basic → vinegar (mild acid) helps.
10. Indicator at endpoint — phenolphthalein pink just after neutralisation in strong acid–base titration (intro).

Write equation: sulphuric acid + sodium hydroxide

Step 1 — H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O (balance H and O).
Step 2 — Salt sodium sulphate; water formed.
Step 3 — Heat evolved — exothermic neutralisation.
Step 4 — Product solution neutral if equimolar strong acid and base.
Conclusion: neutralisation produces sodium sulphate and water.

• Forgetting to balance water and salt coefficients (H₂SO₄ needs 2 NaOH).
• Misconception: neutralisation always gives pH exactly 7 (weak acid/base salts differ).
• Confusing neutralisation with dilution.
• Using strong base on skin for acid burn without water first (NCERT safety).
• Thinking all salts from neutralisation are neutral (see acidic/basic salts).

• Write general word equation for neutralisation.
• Why are antacids taken for indigestion?
• HCl + KOH → ? (products)
• Is neutralisation exothermic or endothermic?

Open the Practice tab for graded questions on Neutralisation.