The limestone cycle
Calcium carbonate
Calcium carbonate, calcium oxide and calcium hydroxide are all made from limestone and have important applications so it is important to know how they are made.
Calcium carbonate is found naturally in A type of sedimentary rock.. When limestone is heated strongly, the calcium carbonate it contains absorbs heat (Reaction in which energy is taken in.) and If a substance decomposes, it breaks down into simpler compounds or elements. to form calcium oxide. This is indicated by an orange glow as the limestone is heated.
calcium carbonate → calcium oxide + carbon dioxide
CaCO3(s) → CaO(s) + CO2(g)
Calcium oxide (also known as quicklime) is a key ingredient in the making of cement and is also used to make certain types of plaster.
Calcium oxide
Calcium oxide reacts with a few drops of water to form calcium hydroxide, which is an A base which is soluble in water.. This is an Reaction in which energy is given out to the surroundings. The surroundings then have more energy than they started with so the temperature increases. reaction, indicated by the water turning to steam. The solid remains white but crumbles into a powder as the water is added.
calcium oxide + water → calcium hydroxide
CaO(s) + H2O(l) → Ca(OH)2(s)
Calcium hydroxide
Calcium hydroxide (also known as slaked lime) is used to To be made neutral by removing any acidic or alkaline nature. excess acidity, for example, in lakes and soils affected by Rain that contains dissolved acidic gases such as nitrogen oxides and sulfur dioxide..
Calcium hydroxide dissolves in excess water to produce calcium hydroxide solution (limewater), which is used to test for carbon dioxide. The carbon dioxide reacts with the calcium hydroxide to form white calcium carbonate, which is insoluble and so turns the limewater ‘milky’.
calcium hydroxide + carbon dioxide → calcium carbonate + water
Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)
All of these reactions are linked together and form the limestone cycle.