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Chapter 7 — Chapter 7 — Acid Base Chemistry

6 topics + Exercise· CHEMISTRY — 9
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Topic 1 · pp. 93–95 · Free

Acids and Bases: Occurrence and Properties

Source: Chemistry 9 (PCTB), Ch 7, pp. 93–95

📘Easy summary

Acids taste sour and turn blue litmus red (lemon, curd, tamarind). Natural (organic) acids come from natural sources; mineral acids (HCl, H₂SO₄, HNO₃) are made from minerals. Bases taste bitter, feel slippery and turn red litmus blue. An alkali is a water-soluble base (NaOH, KOH, Ca(OH)₂, NH₄OH). Metal oxides (Na₂O, CaO, ZnO, MgO) are basic. Acid + base → salt + water (neutralization).

⭐Key points

  • Acetic–vinegar; ascorbic–amla, guava; citric–lemon, orange; lactic–sour milk, curd; formic–ant sting; oxalic–tomato; tartaric–tamarind.
  • Na₂O + H₂O → 2NaOH.
  • Oxalic acid (H₂C₂O₄): simplest organic diprotic acid; bleaching straw, removing rust and ink stains.

🔬Diagram

Acids vs basesAcidsBasesSourBitter, slipperyBlue litmus → redRed litmus → blueH₃O⁺ in waterOH⁻ in water

🌿Real-life example

Formic acid causes the pain of an ant sting.

💡Exam tip

  • Learn Table 7.1 — MCQs on sources (oxalic → tomato).

✅Quick check

1. Oxalic acid source:

2. An alkali is a base that:

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