Notes on the uses of limestone and its products

GCSE Science

Indirect Uses of Limestone:

Lime:

Manufacture

Thermal decomposition is used.
When calcium carbonate is heated strongly, it slowly disassociates into calcium oxide and carbon dioxide.
This reaction takes place in a lime kiln.
It is a reversible direction depending on the pressure and temperature.

CaCO3(s) → CaO(s) + CO2(g)

(reversible)

Uses of lime(CaO):

Used as a drying agent.
To manufacture soda glass(ny heating it with sdium carbonate)
Alos used to make slaked lime. (Ca(OH)2)

Slaked lime(Calcium hydroxide)

Manufacture

Made by adding an equal amount of water to calcium oxide.
This reaction is carefully monitored.
Thius control is needed as it is a highly exothermic reaction.

CaO(s) + H20(l) → Ca(OH)2(s)

Uses

Cheap industrial alkali.
Used to reduce soil acidity
Used in the manufacture of white wash.
Used in glass manufacture and water purification.
Limestone, a weak soln. of slaked lime is used to test for carbon diocide gas.
Calcium Hydroxide is mixed with sand to give mortar.
When mixed with water, it forms a ...

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Slaked lime(Calcium hydroxide)

Manufacture

Made by adding an equal amount of water to calcium oxide.
This reaction is carefully monitored.
Thius control is needed as it is a highly exothermic reaction.

CaO(s) + H20(l) → Ca(OH)2(s)

Uses

Cheap industrial alkali.
Used to reduce soil acidity
Used in the manufacture of white wash.
Used in glass manufacture and water purification.
Limestone, a weak soln. of slaked lime is used to test for carbon diocide gas.
Calcium Hydroxide is mixed with sand to give mortar.
When mixed with water, it forms a strongly bonded material, in order to hold the bricks.
To remove acidic flue gases such as so2, produced when sulphur compounds in fossil fuels burn; the removal of so2 from flue gases is called desulphurization.

Test fpr CO2

Limewater turns milky in presence of controlled amt of CO2, forming calcium carbonate which is cloudy.

Ca(OH)2(aq) + CO2 → CaCO3(s) + H20(l)

If too much of C02 is bubbled however, it becomes colorless once again, forming calcium hydrogen carbonate, which is colorless.

CaCO3(aq) + CO2 → Ca(HCO3)2(aq)

Carbonates & Hysrogencarbonates

Uses of limestone:

Manufacture of iron and steel.

Used in the blast furnace to remove earthly and sandly materials; forming a aliquid slag.

Manufactuire of xcemenr and concrete.

Limestone is mixed with clay in a hethed rotary kiln, using coal or oil as the fuel. The material produced is called cement. It contains a mixture of calcium aluminate and calcium silicate.

The dry product is ground to powder and caso4 is added to slow down the setting. When water is added to this mixture,. Slow complex chemical changes occur and a hard ingterlocking mass of crystals of hydrated calcium aluminate and silicate.

Concrete is a mixture of cement with stone chippings and sand. After these ingredients are poured into water, they are poured into wooden moulds and allowed to set hard.

Reinforced concrete is bhy allowing concrete to set around steel rods to give it greater tensile strength, which is reqd for tge cconstruction of large bridges and builfings.