Extraction of Metals

Question 1

How does the reactivity of a metal affect its extraction?

Answer 1

More reactive the metal, more difficult it is to extract from its ore.

Question 2

What method of extraction can be used for extracting more reactive metals?

Answer 2

Electrolysis

Question 3

What is an example of a more reactive metal?

Answer 3

Aluminium

Question 4

What method of extraction can be used for extracting less reactive metals?

Answer 4

Reduction

Question 5

What is an example of a less reactive metal?

Answer 5

Iron

Question 6

What is phytomining?

Answer 6

Use of plants to absorb metal compounds from soil as part of metal extraction.

Question 7

What are the steps involved in phytomining?

Answer 7

1. Plants very good at absorbing metal compounds through their roots are grown on ground containing low-grade ores, so metal is removed from ore and enters plant.
2. Plants are harvested, dried and burnt to produce ash rich in metal compounds.
3. Acid such as sulfuric acid added to ash and insoluble metal compounds react to produce solution containing soluble copper compounds (leachate).
4. Metal can be obtained by adding scrap iron to leachate solution, displacement reaction will occur. Iron is more reactive than copper in solution and so copper is displaced by iron.

Question 8

What is the ionic equation for the displacement reaction of iron and the copper leachate?

Answer 8

Fe(s) + Cu2+(aq) > Fe2+(aq) + Cu(s)

Question 9

What are the advantages of phytomining?

Answer 9

Better for environment.
Produces energy when plants are burnt.
No noise pollution.
No dust pollution.
No transport of rock.
No traffic.
No light pollution.

Question 10

What are the disadvantages of phytomining?

Answer 10

Slow process as plants need to grow.
Supply is seasonal rather than continuous.

Question 11

What are the 3 stages of the blast furnace extraction method?

Answer 11

1. Formation of reducing agent
2. Reduction of iron oxide (haematite)
3. Removal of acidic impurities

Question 12

What is the process of extracting iron from haematite in a blast furnace?

Answer 12

1. Iron ore, coke and limestone placed into blast furnace and hot air blasted through it.
2. Causes coke to react to form carbon dioxide and further reaction turns this into carbon monoxide which is reducing agent.
3. Iron(III) oxide (iron ore) reacts with carbon monoxide and is reduced to form iron and carbon dioxide.
4. Iron is dense and so sinks to bottom of blast furnace where is tapped off.
5. Limestone is thermally decomposed to form calcium oxide.
6. Calcium oxide is basic and reacts with acidic impurities to form molten slag (calcium silicate).
7. Molten slag can be tapped as is less dense than molten iron.

Question 13

What are the word equations for the formation of the reducing agent?

Answer 13

Coke + Oxygen > Carbon dioxide

Carbon dioxide + Coke > Carbon monoxide

Question 14

What is the word equation for the reduction of the iron(III) oxide to iron?

Answer 14

Iron(III) oxide + Carbon monoxide > Iron + Carbon dioxide

Question 15

What are the word equations for the removal of the acidic impurities?

Answer 15

Calcium carbonate > Calcium oxide + Carbon dioxide

Calcium oxide + Silicon dioxide > Calcium silicate

Question 16

At what temperature is the iron formed in the blast furnace molten?

Answer 16

2,000oC

Question 17

What is thermal decomposition?

Answer 17

Breakdown of a substance using heat.

Question 18

What is the main impurity in the iron(III) oxide?

Answer 18

Sand (silicon dioxide)

Question 19

What is slag used for?

Answer 19

Road building

Question 20

What are the uses of iron?

Answer 20

Used in bridges and structures due to its strength.

Pig iron produced in blast furnace is soft and mixed with carbon to produce alloy steel, to increase its strength.