Notes on Acids, Bases, and Salts

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  • Introduction to chemistry topics aligned with the Cambridge IGCSE syllabus.
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Preparing Insoluble Salts

  • Process: Preparation of insoluble salts uses precipitation.
    • Steps:
    1. Dissolve known amounts of two soluble salts in distilled water using separate beakers.
    2. Mix the two solutions to initiate a reaction producing an insoluble salt.
    3. The insoluble salt precipitates out of the solution as a solid.
    4. Filter to separate the solid precipitate from the liquid solution (filtrate).
    5. Wash the precipitate with distilled water to eliminate soluble impurities.
    6. Dry the purified precipitate in an oven.
  • Example: Preparation of barium sulfate.
    • Reactants: barium chloride and sodium sulfate.
    • Reaction:
      ext{BaCl}2 (aq) + ext{Na}2 ext{SO}4 (aq) ightarrow ext{BaSO}4 (s) + 2 ext{NaCl} (aq)
    • Solid product: barium sulfate ( ext{BaSO}_4) precipitates; sodium chloride ( ext{NaCl}) remains in solution.

Solubility Rules

  • General Rules:
    1. All sodium, potassium, and ammonium salts are soluble.
    2. All nitrates are soluble.
    3. Chlorides are soluble except for lead chloride and silver chloride.
    4. Sulfates are generally soluble, with exceptions for barium sulfate, calcium sulfate, and lead sulfate.
    5. Sodium, potassium, and ammonium carbonates are soluble; other carbonates are insoluble.
    6. Sodium, potassium, and ammonium hydroxides are soluble; calcium hydroxide is partially soluble, all others are insoluble.

Hydrated & Anhydrous Substances

  • Definitions:
    • Anhydrous Substance: Lacks water; crystallizes without it (e.g., sodium chloride).
    • Hydrated Substance: Contains water as part of its crystal structure (e.g., hydrated copper(II) sulfate).
  • Water of Crystallization: Water molecules chemically combined in hydrated crystals.
  • Formula Representation:
    • Example of separated formulas: ext{CuSO}4 ullet 5 ext{H}2 ext{O} for hydrated copper(II) sulfate.
  • Heating Effect:
    • When heated, hydrated copper(II) sulfate releases water to become anhydrous copper(II) sulfate, a reversible reaction:
    • ext{CuSO}4 ullet 5 ext{H}2 ext{O} (s)
      ightarrow ext{CuSO}4 (s) + 5 ext{H}2 ext{O} (g)

Conclusion

  • Final thoughts on completing Chapter 7: Acids, Bases, and Salts.
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