Acids + alkalis

• An acid is a substance produces hydrogen ions when dissolved in water.
• Hydrochloric acid - HCI
• sulfuric acid - H2SO4
• nitric acid - HNO3
• stomach acid -corrosive
• acid in car batteries - corrosive
• found in fizzy drinks


  carbonic acid
• citric aid


  fruit juice
• lemon juice


  flavour
• vinegar


  flavour
• a base is


  a substance that reacts with an acid to neutralize it
• metal oxide

  copper oxide
• metal hydroxide

  magnesium hydroxide
• metal carbonates

  copper carbonate
• metal hydrogen carbonate

  zinc hydrogen carbonate
• an alkali is

  a substance which produces hydroxide ions when dissolved in water
• sodium hydroxide

  NaOH
• potassium hydroxide

  KOH
• oven cleaner

  corrosive
• slaked lime

  corrosive
• weak alkalis

  ammonia and milk of magnesia
• indicator


  a substance that changes colour in the presence of an acid or alkali
• red cabbage

  • acid - pink/red
• red cabbage

  • alkali - green/yellow
• beetroot

  • alkali - yellow
• beetroot

  • acid - red/purple
• blackcurrant

  • alkali - green
• blackcurrant

  • acid - red
• the problem with litmus is

  it doesn't tell you the strength (pH) of an acid or an alkali
• universal indicator doesn't tell you

  the strength pH of an acid or alkali
• phenolphthalein indicator

  • colourless in acid
  • colourless in neutral solutions
  • pink in alkali
• methyl orange indicator

  • red in acid
  • orange in neutral solutions
  • yellow in alkali
• strong acids react faster as

  there's more hydrogen ions in solution
• Neutralisation is

  When hydrogen ions from an acid join up with hydroxide ions from an alkali to form water
• $H +$$OH =$$H20$
• Toothpaste is weakly alkaline so it neutralises acids in your mouth to prevent tooth decay
• wasp sting is weakly alkaline so a weak acid eg vinegar will neutralise it
• bee sting is weakly acidic so a weak alkaline eg baking soda will neutralise it
• soil can be too acidic so a farmer will add lime (calcium hydroxide) to neutralise the souk
• indigestion happens when there is too much acid in the stomach so indigestion tablets which are weakly alkaline are taken to neutralise the excess acid