Acids/Bases/Salts

• Indicators


  Chemical substances that give a colour change in acid, alkali and neutral conditions
• Indicator colour changes


  • Acid - Red
  • Neutral - Red
  • Alkali - Blue
• Litmus indicator colour changes

  • Acid - Red
  • Neutral - Red
  • Alkali - Blue
• Universal indicator


  Gives indication of strength of acids/alkalis
• Universal indicator colour changes

  • Strong acid - Red (0-2)
  • Weak acid - Orange, yellow (3-4-5-6)
  • Neutral - Green
  • Weak alkali - Purple, blue-green (8-9-10-11)
  • Strong alkali - Purple (12-14)
• Best way of men value to 1 d.p.
• More accurate.
• Acids


  Dissolve in water to produce H+ ions
• The higher the H+ concentration


  The lower the pH
• Strong Acids


  Fully ionise in water
• Weak Acids


  Partially ionise in water
• Alkalis


  Dissolve in water to produce OH- ions
• Strong Alkalis


  Completely ionise in water
• Weak Alkalis


  Partially ionised in water
• Weak Alkalis


  • NH3 (Ammonia)
• Base


  Neutralises an acid
• Alkali


  A soluble base
• Reactions of Acids


  1. Acid + Base (Neutralisation) → Salt + Water

  2. Exothermic reaction
• Salt


  A compound formed when the hydrogen ions in an acid are replaced by metal ions