C1 - Limestone

Question 1

What is the formula for limestone?

Answer 1

CaCO3

Question 2

What is produced when limestone is heated strongly?

Answer 2

CaCO3 -> CaO + CO2.

Question 3

What are the chemical and everyday names of CaO and Ca(OH)2(s) and Ca(OH)2(aq)?

Answer 3

CaO is calcium oxide or quicklime. Ca(OH)2(s) is calcium hydroxide or slaked lime, Ca(OH)2(aq) is calcium hydroxide or limewater.

Question 4

What type of reaction is CaCO3 -> CaO + CO2?

Answer 4

Thermal decomposition (heat is used to break down a compound)

Question 5

What is limestone used for?

Answer 5

Building material, statues, abrasive in toothpaste, cement, and mortar and concrete.

Question 6

Limestone is thermally decomposed inside a rotatory kiln. Explain why large amounts of CO2 are produced in this process.

Answer 6

Thermal decomposition of limestone releases CO2. The fuel that is combusted to produce the high heat required (methane), releases CO2.

Question 7

One of the waste gases leaving the limekiln is nitrogen. Where does this gas come from?

Answer 7

From the hot air that is blast into the kiln to provide the heat needed for thermal decomposition. Air contains 78% nitrogen.

Question 8

Not all metal carbonates decompose when heated with a Bunsen flame. Give a reason for this.

Answer 8

They require a higher temperature to break the bonds present in the compound.

Question 9

How do you test for carbon dioxide?

Answer 9

Bubble the gas through limewater. If carbon dioxide is present, the limewater will turn cloudy as finely suspended calcium carbonate precipitate is produced.

Question 10

What is produced when metal carbonates such as calcium carbonate react with acids?

Answer 10

Salt, water and carbon dioxide; for example magnesium

carbonate + hydrochloric acid -> magnesium chloride + water + carbon dioxide

Question 11

Write equations for the limestone cycle

Answer 11

CaCO3(s) -> CaO(s) + CO2(g)
CaO(s) + H2O(l) -> Ca(OH)2(s)
Ca(OH)2(s) + more water -> Ca(OH)2(aq)
Ca(OH)2(aq) + CO2(g) -> CaCO3(s) + H2O(l)

Question 12

Buildings made from limestone are affected by burning fossil fuels containing sulfur Explain why.

Answer 12

The sulphur reacts with oxygen when the fuel is burnt.

This produces sulphur dioxide which dissolves in rain water producing acid rain which reacts with limestone.

Question 13

Calcium carbonate reacts with sulphuric acid. Use the
equation to explain why the reaction stops quickly:
CaCO3(s) + H2SO4(aq) -> CaSO4(s) + H2O(l) + CO2(g)

Answer 13

A layer of CaSO4 forms around the CaCO3. This layer prevents the acid from reacting further with the CaCO3, so the reaction stops.

Question 14

Plaster is made by mixing slaked lime with water. Why does plaster become hard over time?

Answer 14

Plaster is Ca(OH)2(aq). When it is exposed to air, it reacts with CO2 in the air and forms solid CaCO3 and H2O. The water evaporates.

Question 15

How do you produce mortar?

Answer 15

By mixing cement with water and sand.

Question 16

Why does mortar hold bricks together?

Answer 16

The calcium hydroxide reacts with the carbon dioxide in the air, forming solid limestone which holds the bricks together.

Question 17

What are the disadvantages of mortar and cement?

Answer 17

Large amounts of CO2 are produced when making cement and mortar.

Question 18

How do you make cement?

Answer 18

Heat limestone with clay in a kiln.

Question 19

How do you make concrete?

Answer 19

Add water, cement, sand and small stones or crushed rock.

Question 20

Why do builders use concrete rather than pure cement?

Answer 20

Pure cement would be too expensive.

Question 21

Give reasons for using concrete rather than limestone as a building material.

Answer 21

Can be poured into shapes, weather and corrosion resistant, stronger.

Question 22

Give reasons against building with concrete.

Answer 22

Ugly; production releases carbon dioxide which adds to the greenhouse effect.

Question 23

Give reasons for mining limestone.

Answer 23

Many uses, especially as a building material; mining provides jobs, workers will move to local area improving the local economy.

Question 24

Give reasons against mining limestone.

Answer 24

Destruction of habitats; air pollution (CO2) from lorries driving to and from the mine; noise and dust pollution; tourists stay away.