Limestone Cycle

• Limestone cycle

  
• Limestone cycle

  
• Reaction 1:

  Thermal decomposition of calcium carbonate (limestone)

  • CaCO3 (heat) -> CaO + CO2
  • Limestone -> calcium oxide (quicklime) + carbon dioxide

  Observation - limestone shining orange (limestone glows when heated).
• Reaction 2:

  Hydration of calcium oxide (quicklime) with water

  • CaO + H2O -> Ca(OH)2
  • Calcium oxide (quicklime) + water -> calcium hydroxide (slaked lime)

  Observation - hissing / fizzing (steam produced), popping, temperature increase, solid crumbling - exothermic reaction
• Reaction 3:

  Dilution of concentrated calcium hydroxide (slaked lime)

  • Ca(OH)2 (concentrated) + H2O -> Ca(OH)2 (diluted)
  • Calcium hydroxide (slaked lime) + water -> calcium hydroxide (limewater)
• Reaction 4:

  • Ca(OH)2 (diluted) + CO2 -> CaCO3
  • Calcium hydroxide (limewater) + carbon dioxide -> calcium carbonate (limestone)

  Observation - precipitate forms and turns limewater milky

  Converted back to calcium carbonate