Using Limestone

Question 1

How is limestone often formed?

How is it found?

Answer 1

From sea shells.

It is usually quarried out of the ground.

Question 2

What is limestone mainly?

Answer 2

Limestone is mainly calcium carbonate- CaCO3.

Question 3

What happens to limestone when it is heated?

Answer 3

It thermally decomposes to make calcium oxide and carbon dioxide.

Calcium carbonate → calcium oxide + carbon dioxide

CaCO3 → CaO + CO2

Magnesium, copper, zinc and sodium carbonates decompose in the same way once heated.

A bunsen burner cannot reach a high enough temperature to thermally decompose some carbonates of group 1 metals.

Question 4

How limestone is damaged by acid rain.

Answer 4

Calcium carobnate reacts with acid to make calcium salt, carbon dioxide and water.

CaCO3→ sulfuric acid+ calcium sulphate+ carbon dioxide + water

CaCO3 + H2SO4 → CaSO4 + CO2 + H2O

• The type of salt produced depends on the type of acid. For example, a reaction with hydrochloric acid would make a chloride (e.g. CaCl2)
• Other carbonates that react with acids are magnesium, copper, zinc and sodium.

Question 5

What happens when you add water to calcium oxide?

Answer 5

You get calcium hydroxide.

Calcium oxide + water → calcium hydroxide

CaO + H2O → Ca(OH)2

• Calcium hydroxide is an alkali used to neutralise acidic soil in fields (Powdered limestone can be used for this too but calcium hydroxide is faster).

Question 6

What is the test for water?

Answer 6

Calcium hydroxide can be used in a test for carbon dioxide.

A solution of of calcium hydroxide in water (called limewater) and bubble gas through it, the solution will turn cloudy if there’s carbon dioxide in the gas. The cloudiness is caused by the formation of calcium carbonate.

Calcium hydroxide + carbon dioxide → calcium carbonate + water

Ca(OH)2 + CO2 → CaCO3 +H2O

Question 7

Uses of limestone:

Answer 7

• making into blocks for building like cathedrals
• Powdered limestone is heated in a kiln with powdered clay to make cement. - cement can be mixed with sand and water to make mortar. Mortar is the stuff used to stick bricks together with.
• Mix cement with sand and aggregate (water and gravel) to make concrete.

Question 8

Quarrying limestone:

Answer 8

• Digging limestone can cause environmental problems
• makes huge holes which permenantly disfigure the landscape
• quarrying process like blasting rocks apart, makes lots of noise and dust in quite, scenic areas.
• destroys the habitats of animals.
• limestone needs to be trnsported away from the quarry- usually in lorries causing more noise and pollution.
• Waste materials produce unsightly tips.

Making stuff rom limestone also causes pollution, for example:

• Cement factories make a lot of dust, which can cause breathing problems.
• Energy is needed to to produce cement and quicklime. The energy is most likely from burning fossil fuels, which causes pollution.

Question 9

Advantages of using limestone:

Answer 9

• provides things that people want such as houses and roads.
• chemicals used in dyes, paints and medicines come from limestone.
• products are used to neutralise acidic soil such as acid in lakes and rivers.
• used in power station chimney to neutralise sulphur dioxide (which is the cause of acid rain).
• the quarry and businessess provide jobs for people and bring money into the local economy.
• once quarrying is complete, landscaping and restoration is normally required.
• widely available and cheaper than granite and marble (also hardwearing)
• does not rot and fire resistant.