C1 2 Limestone Flashcards
What is the reaction called where limestone is heated strongly to form calcium oxide and carbon dioxide?
A thermal decomposition reaction.
What is limestone mainly made out of?
Limestone is mainly made out of calcium carbonate.
What is a rotary lime kiln?
A rotary lime kiln is where lots of calcium oxide is made from the thermal decomposition of calcium carbonate. The limestone is thoroughly mixed with hot air and steam.
What happens when carbonates react with acids?
A salt, water and carbon dioxide forms.
Testing for carbon dioxide
Carbon dioxide turns limewater solution cloudy/ milky white. Carbon dioxide is weakly acidic so it reacts with the alkaline limewater. Insoluble calcium carbonate is formed as the precipitate.
Calcium carbonate + hydrochloric acid —> ?
Calcium chloride + water + carbon dioxide.
Calcium carbonate (+heat) —> ?
Calcium oxide + carbon dioxide. This is the thermal decomposition of calcium carbonate.
Calcium hydroxide + carbon dioxide —>?
Calcium carbonate (insoluble precipitate) + water. This is the test for carbon dioxide.
What happens when water is added to calcium oxide?
We get calcium hydroxide formed. This reaction gives out a lot of heat (exothermic).
Describe the limestone cycle:
•Calcium carbonate is thermally decomposed to give calcium oxide (quicklime). Carbon dioxide is released. • A little water is added to the calcium oxide to give calcium hydroxide (slaked lime). •More water is added and the solution is filtered. We get calcium hydroxide solution (limewater). • Carbon dioxide is added which is a test for carbon dioxide and we return with our calcium carbonate again.
How is cement made?
Cement is made by heating limestone with clay in a kiln.
How is mortar made?
Mortar is made by mixing cement and sand with water.
How is concrete made?
Concrete is made by mixing crushed rocks called aggregates with cement and sand with water.
Development of lime mortar:
The Egyptians heated limestone strongly in a fire to get calcium oxide which they reacted with water. This hardened with age. This calcium hydroxide was used to plaster pyramids. Later, they mixed this calcium hydroxide with sand and water to produce mortar.
How does mortar work?
Mortars work by the lime in the mortar reacting with carbon dioxide in the air, producing calcium carbonate again. This means that the rocks are held together effectively by rock. The amount of sand is also important. Too much sand makes the sand weak but too little makes the mortar shrink as it dries.
Limestone Cycle
