Uses of Limestone
What is limestone?
- Limestone is a sedimentary rock.
- It is very slippery.
- It contains 50% calcuim carbonate (CaCO3), since the solution of calcuim carbonate is lime water.
- It is used for building, cement and chalk.
- We obtain it by quarrying.
When heated strongly calcuim carbonate decomposes to make calcuim oxide and carbon dioxide. This is done on a large scale in lime kilns. the equation for this reaction is:
CaCO3 ------------ CaO + CO2
This type of reaction is called thermal decomposition. This means 'breaking down by heating'.
Reactions of Carbonates
All metal carbonates react in similar ways when heated or when reacted with acids. Metal carbonates decompose when strongly heated to produce the metal oxide and carbon dioxide. Bunsen burner flames do not get hot enough to decompose sodium or potassium carbonate.
Salt, water and carbon dioxide gas are produced when all carbonates react with acids. Limestone is damaged by acid rain because the calcuim carbonate in the limestone reacts with acids in the rain.
Calcium hydroxide solution is known as limewater. This is used to test for carbon dioxide. The limewater turns cloudy because it reacts with carbon dioxide to produce insoluble calcium carbonate.
Insoluble - A substance uncapable of dissolving.
The word equation for the reaction of magnesium carbonate with bydrochloric acid is:
magnesium + hydrochloric acid → magnesium chloride + hydrogen
The Limestone Cycle
When heated strongly the calcuim carbonate in limestone decomposes to calcium oxide and carbon dioxide. When water is added to calcium oxide they react to produce calcuim hydroxide.
Calcium hydroxide is an alkali and so it can be used to neutralise acids. For example, it is used by farmers to neutralise acidic soild and in industry to neutralise acidic gases.
Calcium oxide is not very soluble in water but dissolves slightly to make limewater.Calcium hydroxide reacts with carbon dioxide to produce calcium carbonate, the main compound in limestone. Soluble - ability to dissolve, especially in water.
Equations for reactions in the limestone cycle:
1. CaCO3 -------- CaO + Co2
2. Cao + H2O -------- Ca(OH)2
3. Ca(OH)2 + Co2 -------- CaO
Cement and Concrete
To make cement limestone is mixed with clay and heated strongly in a kiln. The product is ground up to make a fine powder.
Cement is mixed with sand and water to amke mortar. The mortar is used to hold together bricks and blocks in buildings.
Concrete is made by adding aggregate to cement, sand and water. Small stones or crushed rock are used as aggregate. The mixture is poured into moulds before it sets and hardens.
What are the differences between cement, mortar and concrete? Cement is very easy/ accesable to make. Concrete is made using cemnet and other products. Mortar does not need heat to be made.
Limestone is depended on for building and for building materials. Cement and concrete are needed in most buildings. Quarrying limestone can have negative impacts on the environment and on people living nearby.
Cement works are often close to limestone quarries. making cement involves heating limestone with clay in large kilns. This uses a large area of land and ALOT of energy.
Advantages of quarrying:
- There is more employment and oppourtunities for local people.
- More customers and trade for local buisnesses.
- Improved roads.
Disadvantages of quarrying:
- There is alot of dust and noise.
- There will be more traffic.
- Loss of habitats for wildlife.