Sunday, March 1, 2009

only for gcse chemistry -Chemical from calcium carbonate

Thermal decomposition of calcium carbonatecalcium carbonate ---heat---> calcium oxide + carbon dioxideCaCO3(s) ---heat---> CaO(s) +CO2(g)(limestone) (quicklime)

Water and calcium oxidecalcium oxide + water ---> calcium hydroxideCaO(s) + H2O(l) ---> Ca(OH)2(s) (slaked lime) looks flaky and gets hotWith more water the calcium hydroxide dissolves to make limewater Ca(OH)2(aq)
Neutralising soil acidityCalcium oxide and calcium hydroxide are bases. (like all metal oxides and hydroxides)acid + base ---> salt + waterso acid soil is neutralised by calcium oxide or calcium hydroxidee.g. nitric acid + calcium oxide --> calcium nitrate + water

2HNO3(aq) + CaO(s) ---> Ca(NO3)2(aq) +H2O(l)Farmers can add calcium oxide or calcium hydroxide to their acid soil to neutralise it.The neutral soil is better for growing plants.Task C3.25 Write word equations and balanced chemical equations for neutralising the following acids using calcium oxide and calcium hydroxide: nitric acid, sulphuric acid, hydrochloric acid, phosphoric acid (H3PO4)

Uses of calcium carbonateCement is made from calcium carbonate (limestone).limestone --heat--> calcium oxide + carbon dioxide

Calcium oxide + clay ----> cementGlass is made using calcium carbonate.

Calcium carbonate + sand + sodium carbonate ---heat--> glassIron is manufactured using calcium carbonate in the blast furnace.calcium carbonate --heat--> calcium oxide + carbon dioxideCalcium oxide + silicon dioxide ----> calcium silicate (mostly sand) (slag) (floats on top of molten iron)

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