Carbon Dioxide

• FORMULA: CO2
• PHYSICAL PROPERTIES:

  1. Colourless
  2. Odourless gas
  3. Slightly soluble in water
  4. Acidic
  5. Denser than air
• TEST FOR CARBON DIOXIDE:

  1. Bubble the gas though colourless limewater
  2. Carbon Dioxide turns limewater milky

  Limewater is calcium hydroxide

  Calcium carbonate is insoluble so a precipitate occurs

  CO2 + Ca(OH)2 -> CaCO3 + H2O

  IN EXCESS, the precipitate disappears and colourless solution is formed

  formation of soluble calcium hydrogen carbonate

  CaCO3 + CO2 +H2O -> Ca(HCO3)2
• PREPARATION OF CARBON DIOXIDE:

  Calcium carbonate = marble chips

  Calcium carbonate + dilute hydrochloride acid -> Calcium chloride + carbon dioxide + water

  CaCO3 + 2HCl -> CaCl2 + CO2 + H2O

  OBSERVATIONS:

  1. Colourless gas is given off
  2. calcium carbonate disappears
  3. fizzing
  4. heat is given off

  CO2 collected by Downward delivery as it is heavier than air
• Draw diagram of preparation of carbon dioxide:

  Diagram

  
• USES OF CARBON DIOXIDE:

  1. Fire extinguishers as it does not support combustion as it is denser than air so sinks over flames and starves the fire of oxygen
  2. Fizzy drinks -> low solubility in water
  3. Dry Ice is solid carbon dioxide, keeps food cold (sublimes when heated)
• CHEMICAL REACTIONS OF CO2:

  reacts with water forming carbonic acid, a weak acid

  CO2 + H2O -> H2CO3

  acid cannot be isolated from solution. Acidity in fizzy drinks