Limestone is mainly calcium carbonate, CaCO3. When it is heated, it breaks down to form calcium oxide and carbon dioxide. Calcium oxide reacts with water to produce calcium hydroxide.
Limestone and its products have many uses, including being used to make mortar, cement, concrete and glass.
Metal carbonates such as calcium carbonate break down when heated strongly. This is called thermal decomposition. Here are the equations for the thermal decomposition of calcium carbonate:
calcium carbonate calcium oxide + carbon dioxide
CaCO3 CaO + CO2
Other metal carbonates decompose in the same way. Here are the equations for the thermal decomposition of copper carbonate:
copper carbonate copper oxide + carbon dioxide
CuCO3 CuO + CO2
Notice that in both examples the products are a metal oxide and carbon dioxide. The carbon dioxide gas can be detected using limewater. Limewater turns cloudy white when carbon dioxide is bubbled through it.
Metals high up in the reactivity series - such as calcium - have carbonates that need a lot of energy to decompose them. Metals low down in the reactivity series - such as copper - have carbonates that are easily decomposed. This is why copper carbonate is often used at school to show these reactions. It is easily decomposed, and its colour change, from green copper carbonate to black copper oxide, is easy to see
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