Limestone Cycle

Question 1

Uses of limestone

Answer 1

Paving
Clippings / clippings in roads
Neutralise acidic lakes

Question 2

Limestone cycle / thermal decomposition equation

Starting step

Answer 2

Calcium carbonate (limestone) -> calcium oxide + carbon dioxide

Question 3

Next step

Answer 3

Add water

Calcium oxide+ water -> calcium hydroxide

Question 4

Third step

Answer 4

Now add lots more water to get limewater ( a solution of calcium hydroxide)

Finally bubble through carbon dioxide
Calcium hydroxide+ carbon dioxide -> calcium carbonate + water (limestone)
Back to limestone, therefore a cycle!

Question 5

Testing for CO2 with limewater

Answer 5

Limewater is calcium hydroxide solution

The reason limewater goes cloudy when you add carbon dioxide is the calcium carbonate forming

Question 6

Limestone cycle summary

Answer 6

When limestone (calcium carbonate) is heated strongly, it decomposes to give solid quicklime (calcium oxide) and carbon dioxide gas. When a small amount of water is added to quicklime it gives slaked lime (calcium hydroxide). If a lot of water is added to slaked lime, a solution of limewater or calcium hydroxide is formed. If carbon dioxide is bubbled through lime water , limestone is formed again along with water.

Question 7

Uses of calcium oxide

Answer 7

Used in Making porcelain and glass

In purifying sugar and preparing bleaching powder

Question 8

Uses of calcium hydroxide

Answer 8

Used in sewage treatment, paper production and food processing