Properties of Acids and Alkalis

6.1 Properties of Acids and Alkalis

Properties of Acids vs Alkalis

• Acids

  • pH value less than 7
  • Taste sour
  • Corrosive
  • Turns blue litmus paper red
  • Reacts with metals to produce hydrogen gas

• Alkalis

  • pH value more than 7
  • Taste bitter
  • Corrosive
  • Turns red litmus paper blue
  • Does not react with metals

Acidic and Alkaline Substances

• Examples:

  • Acidic substance: Vinegar
  • Alkaline substance: Soap

• Indicators: Substances that change color to identify whether a solution is acidic or alkaline.

  • Phenolphthalein

    • Acid & Neutral: Colourless
    • Alkali: Pink

  • Universal Indicator

    • Acid: Red
    • Neutral: Green
    • Alkali: Blue

  • Methyl Orange

    • Acid: Red
    • Neutral and Alkali: Yellow

  • Blue Litmus Paper

    • Acid: Red
    • Neutral and Alkali: Blue

  • Red Litmus Paper

    • Acid and Neutral: Red
    • Alkali: Blue

Strength of Acids and Alkalis

• The pH scale is used to determine the strength of acids or alkalis.
  • Acid strength: Lower pH value indicates a stronger acid.
  • Alkali strength: Higher pH value indicates a stronger alkali.

Uses of Acids and Alkalis in Daily Life

• Acids:

  1. Tartaric acid
  2. Fizzy drinks: Carbonic acid
  3. Car batteries: Sulphuric acid
  4. Pickles: Vinegar

• Alkalis:

  1. Soap: Potassium hydroxide
  2. Fertilizers: Ammonia
  3. Detergents: Sodium hydroxide
  4. Antacid pills: Magnesium hydroxide