13. Carbonates Flashcards
What does limestone mainly consist of?
Limestone consists mainly of calcium carbonate, CaCO3
What is lime?
calcium oxide
How is lime made?
manufactured from calcium carbonate by thermal decomposition:
What is the chemical equation for the thermal decomposition of limestone?
CaCO3 → CaO + CO2
What is slaked lime?
calcium hydroxide
How is calcium hydroxide made?
made by adding a small amount of water slowly to calcium oxide
What is the chemical equation for the manufacture of slaked lime?
CaO + H2O → Ca(OH)2
What is limewater?
Limewater is a solution of calcium hydroxide in water
is limewater acidic or alkaline?
alkaline
What is formed when carbon dioxide is added to limewater?
The addition of carbon dioxide to calcium hydroxide produces the initial starting material, calcium carbonate
What is the chemical equation for the reaction between carbon dioxide and limewater?
CO2 + Ca(OH)2 → CaCO3 + H2O
Why does limewater turn cloudy upon contact with carbon dioxide?
turns cloudy due to calcium carbonate forming, which is an insoluble precipitate and the solution turns milky? cloudy
What do these 3 reactions constitute?
The limestone cycle
What does limestone help the manufacture of? 2
Limestone (calcium carbonate) is used in the manufacture of iron and cement
How does limestone help in the production of iron?
In the production of iron, limestone is added to the blast furnace where it decomposes to form lime (CaO) and carbon dioxide
The lime reacts with silica impurities to form calcium silicate, which floats to the top of the molten iron and is removed:
CaO + SiO2 → CaSiO3
- How is cement manufactured?
manufacture of cement
Cement is manufactured by heating a mixture of powdered limestone and clay in a rotary kiln
- What is added to the rotary kiln?
manufacture of cement
Once heated, calcium sulfate and water are added which produce cement
- What is cement? What is it made of?
manufacture of cement
Cement is a hardened, interlocked structure of calcium aluminate (Ca(AlO2)2 and calcium silicate (CaSiO3)
How can calcium carbonate be used?
CaCO3 is also used in treating excess acidity in soils and lakes where it is often preferred to lime because it does not make the water in the soil alkaline
how can lime be used?
Lime (calcium oxide) is used in lime mortar and in flue-gas desulfurisation
What does flue gas desulfurisation involve?
Flue-gas desulfurization involves spraying acidic sulfur dioxide emissions with jets of slaked lime to reduce pollution by neutralising these gases before they leave the factory chimneys
What may happen if too much lime is added when treating acidic soils?
It is also used in treating excess acidity in soils and lakes. If excess lime is used, however, the water in the soil may become too alkaline
How can slaked lime be used? 2
Slaked lime (calcium hydroxide) is used in treating acidic soils and neutralising acidic industrial wasted products
