Calcium oxide (Or Quick lime) is a pure compound made of Calcium (Ca+2 )and Oxide(O-2) ions. It is a white crystalline solid with a melting point of 2572°C.


It is manufactured by heating limestone, coral, sea shells, or chalk, which are mainly CaCO3 , to drive off carbon dioxide. Thisreaction isreversible; calcium oxide willreact with carbon dioxide to form calcium carbonate. The reaction is driven to the right by flushing carbon dioxide from the mixture as it is released. 


  • Heat: Quicklime releases Thermal energy by the formation of the hydrate, calcium hydroxide, by the following equation:
CaO (s) + H2O (l)  Ca(OH)2 (aq) (ΔHr = −63.7 kJ/mol of CaO)
As it hydrates, an exothermic reaction results and the solid puffs up. The hydrate can be reconverted to quicklime by removing the water by heating it to redness to reverse the hydration reaction. One litre of water combines with approximately 3.1 kilograms (6.8 lb) of quicklime to give calcium hydroxide plus 3.54 MJ of energy. This process can be used to provide a convenient portable source of heat, as for on-the-spot food warming in a self-heating can.
  • Light: When quicklime is heated to 2,400 °C (4,350 °F), it emits an intense glow. This form of illumination is known as a limelight, and was used broadly in theatrical productions prior to the invention of electric lighting.
  • Cement: Calcium oxide is a key ingredient for the process of making cement.
  • As an alkali in biodiesel production.
  • Petroleum industry: Water detection pastes contain a mix of calcium oxide and phenolphthalein. Should this paste come into contact with water in a fuel storage tank, the CaO reacts with the water to form calcium hydroxide. Calcium hydroxide has a high enough pH to turn the phenolphthalein a vivid purplish-pink color, thus indicating the presence of water.
  • Paper: Calcium oxide is used to regenerate sodium hydroxide from sodium carbonate in the chemical recovery at Kraft pulp mills.
  • Plaster: There is archeological evidence that Pre-Pottery Neolithic B humans used limestone-based plaster for flooring and other uses. Such Lime-ash floor remained in use until the late nineteenth century.
  • Chemical or power production: Solid sprays or slurries of calcium oxide can be used to remove sulphur dioxide from exhaust streams in a process called flue-gas desulfurization.


Consider the below PDF article for more details about Calcium Oxide. File:LIME CalciumOxide.pdf

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