13. Carbonates

Question 1

What does limestone mainly consist of?

Answer 1

Limestone consists mainly of calcium carbonate, CaCO3

Question 2

What is lime?

Answer 2

calcium oxide

Question 3

How is lime made?

Answer 3

manufactured from calcium carbonate by thermal decomposition:

Question 4

What is the chemical equation for the thermal decomposition of limestone?

Answer 4

CaCO3 → CaO + CO2

Question 5

What is slaked lime?

Answer 5

calcium hydroxide

Question 6

How is calcium hydroxide made?

Answer 6

made by adding a small amount of water slowly to calcium oxide

Question 7

What is the chemical equation for the manufacture of slaked lime?

Answer 7

CaO + H2O → Ca(OH)2

Question 8

What is limewater?

Answer 8

Limewater is a solution of calcium hydroxide in water

Question 9

is limewater acidic or alkaline?

Answer 9

alkaline

Question 10

What is formed when carbon dioxide is added to limewater?

Answer 10

The addition of carbon dioxide to calcium hydroxide produces the initial starting material, calcium carbonate

Question 11

What is the chemical equation for the reaction between carbon dioxide and limewater?

Answer 11

CO2 + Ca(OH)2 → CaCO3 + H2O

Question 12

Why does limewater turn cloudy upon contact with carbon dioxide?

Answer 12

turns cloudy due to calcium carbonate forming, which is an insoluble precipitate and the solution turns milky? cloudy

Question 13

What do these 3 reactions constitute?

Answer 13

The limestone cycle

Question 14

What does limestone help the manufacture of? 2

Answer 14

Limestone (calcium carbonate) is used in the manufacture of iron and cement

Question 15

How does limestone help in the production of iron?

Answer 15

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

Question 16

1. How is cement manufactured?

manufacture of cement

Answer 16

Cement is manufactured by heating a mixture of powdered limestone and clay in a rotary kiln

Question 17

2. What is added to the rotary kiln?

manufacture of cement

Answer 17

Once heated, calcium sulfate and water are added which produce cement

Question 18

3. What is cement? What is it made of?

manufacture of cement

Answer 18

Cement is a hardened, interlocked structure of calcium aluminate (Ca(AlO2)2 and calcium silicate (CaSiO3)

Question 19

How can calcium carbonate be used?

Answer 19

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

Question 20

how can lime be used?

Answer 20

Lime (calcium oxide) is used in lime mortar and in flue-gas desulfurisation

Question 21

What does flue gas desulfurisation involve?

Answer 21

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

Question 22

What may happen if too much lime is added when treating acidic soils?

Answer 22

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

Question 23

How can slaked lime be used? 2

Answer 23

Slaked lime (calcium hydroxide) is used in treating acidic soils and neutralising acidic industrial wasted products