Chemical Changes: Neutralisation

Acids and Alkalis

• Acids:

  • Strong Acids:

    Hydrochloric acid → in stomach, removes rust

    Sulfuric acid → car batteries, fertilizers, detergents

    Nitric acid → fertilizers

  • Weak Acids:

    Ethanoic acid → vinegar

    Citric acid → citrus fruits

    Lactic acid → yogurt

• Alkalis:

  • Strong Alkalis:

    Sodium/Potassium hydroxide → soaps, detergents

    Calcium hydroxide → reduces soil acidity

    Aqueous ammonia → fertilizers

Neutralisation

• Definition: The reaction between an acid and a base to form salt and water.
  acid + base \rightarrow salt + water

• Example: Hydrochloric acid + Sodium hydroxide \rightarrow Sodium chloride + Water

• Applications:

  • Slaked lime (calcium hydroxide) reduces soil acidity

  • Milk of magnesia (antacids) reduces stomach acidity

  • Toothpaste neutralizes acids on teeth

• Predicting Salt Produced:

  • Metal/first word of base = first word of salt.

  • Acid used determines ending name of salt (Hydrochloric acid = chloride, Sulfuric acid = sulfate, Nitric acid = nitrate).

Other Reactions of Acids

• With Metals: acid + metal \rightarrow hydrogen + salt

  • Only reactive metals react. Unreactive metals like silver, copper, and gold do not react.

  • Test for Hydrogen Gas:

    • A lighted splint at the mouth of the test tube will be extinguished with a 'pop' sound.

• With Carbonates: acid + carbonate \rightarrow carbon \ dioxide + salt + water

  • Test for Carbon Dioxide Gas:

    • Bubble the gas into limewater; the limewater turns chalky or cloudy (white precipitate).