Acids, Bases & Salts
The pH scale, neutralisation, and salt preparation
pH scale** runs 0–14. **Acids: pH below 7 (HCl, H₂SO₄, HNO₃). **Alkalis/Bases:** pH above 7 (NaOH, KOH, NH₃). **Neutral:** pH 7 (pure water).
Indicators: Litmus (red in acid, blue in alkali). Universal indicator gives a colour range. pH meter = most accurate.
Neutralisation: Acid + Base → Salt + Water
- HCl + NaOH → NaCl + H₂O
- H₂SO₄ + CuO → CuSO₄ + H₂O
Naming salts: The first part comes from the metal/base, second from the acid:
- HCl → chloride salts
- H₂SO₄ → sulfate salts
- HNO₃ → nitrate salts
Reactions of acids:
- Acid + Metal → Salt + Hydrogen gas (zinc + HCl → ZnCl₂ + H₂)
- Acid + Metal carbonate → Salt + Water + Carbon dioxide
- Acid + Metal oxide → Salt + Water
Titration: Used to find the exact volume of acid needed to neutralise a base. Use a **burette** for acid, **pipette** for alkali, indicator shows endpoint.
Key Points to Remember
- 1pH 0-7 acids, pH 7-14 alkalis, pH 7 neutral
- 2Neutralisation: acid + base → salt + water
- 3Salt name: metal name + acid anion (chloride/sulfate/nitrate)
- 4Titration: precise neutralisation using burette and indicator
Pakistan Example
Khewra Salt Mine — Natural Salt Chemistry
The Khewra Salt Mine in Punjab produces rock salt (NaCl) — a neutral salt. But industrial processes need specific salts: copper sulfate (CuSO₄) for electroplating requires H₂SO₄ + CuO neutralisation. Fertiliser factories near Faisalabad produce ammonium nitrate (NH₄NO₃) by neutralising nitric acid with ammonia. Every salt factory in Pakistan is running neutralisation reactions at scale.
Quick Revision Infographic
Chemistry — Quick Revision
Acids, Bases & Salts
Key Concepts
Formulas to Know
Neutralisation: acid + base → salt + waterchloride/sulfate/nitrate)Khewra Salt Mine — Natural Salt Chemistry
The Khewra Salt Mine in Punjab produces rock salt (NaCl) — a neutral salt. But industrial processes need specific salts: copper sulfate (CuSO₄) for electroplating requires H₂SO₄ + CuO neutralisation. Fertiliser factories near Faisalabad produce ammonium nitrate (NH₄NO₃) by neutralising nitric acid with ammonia. Every salt factory in Pakistan is running neutralisation reactions at scale.