The Lime Cycle is one of nature`s best known examples of chemistry. This classic series of chemical reactions is the basis for numerous applications, many of which affect our lives every day.
The image above illustrates how chalk or limestone (calcium carbonate) turns into quicklime after heating, then into hydrated lime (slaked lime or calcium hydroxide) after adding water and finally back into chalk by combining with carbon dioxide from the air.
The reactions involved in lime manufacture are:
Calcining or burning of chalk to produce quicklime
CaCO3 + HEAT = CaO + CO2
Hydration or slaking of quicklime to produce hydrated lime
CaO + H2O = Ca(OH)2
Carbonation of hydrated lime to produce chalk (sometimes known as precipitated calcium carbonate or PCC).
Ca(OH)2 + CO2 = CaCO3
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