Blast Furnace and Extractions

Question 1

Extracting metals that are above carbon in the reactivity series

Answer 1

Must be extracted using electrolysis

Question 2

Extracting metals that are below carbon in the reactivity series

Answer 2

Can be made from their ores by heating them with carbon

Question 3

Main ore of Aluminium

Answer 3

Bauxite - Clay mineral, impure aluminium oxide

Question 4

How is the problem of aluminium’s high temperature solved?

Answer 4

Aluminium oxide dissolved in molten cryolite (a solent)

Decreases required operating temperature

Question 5

Ionic half equation at anode in aluminium extraction

Answer 5

Oxide ion lose electrons to form oxygen gas

2O 2- –> O2 + 4e-

Question 6

Ionic half equation at the cathode in aluminium extraction

Answer 6

Aluminium ions reduced to aluminium by gaining electrons

Al 3+ + 3e- –> Al

Question 7

Aluminium extraction, why do the positive electrodes need to be replaced

Answer 7

Because of the high temperatures, carbon anode burn in oxygen to form carbon dioxide

Question 8

Major cost of aluminium extraction

Answer 8

Lots of electricity needed to make solution molten, due to its high melting point

Question 9

Uses and properties of Aluminium (3)

Answer 9

Aluminium alloys normally used (not very strong)
Pots & pans-shiny, resists corrosion, low density, good conductor of heat
Overhead cables-Resists corrosion, low density, good conductor of electricity

Question 10

Conditions needed for the extraction
Catalyst
Temperature

Answer 10

Catalyst - Cryolite

Temperature - 1000 degrees

Question 11

How is pig iron made

Answer 11

Molten iron straight from furnace is cooled rapidly & solidified by running it through sand moulds

Question 12

How is cast iron made

Answer 12

Pig iron is remelted & cooled under controlled condition (very impure iron)

Question 13

Uses and properties of cast Iron

Answer 13

Castings - Very fluid when molten, doesn’t sjrink when solidified
Very hard but brittle
Man hole covers, guttering and drainpipes

Question 14

Iron ore

Answer 14

Haematite

Fe2O3

Question 15

Blast furnace:

Trends of boiling point and viscosity of main fractions

Answer 15

Further down column, molecules:
Are larger
Have higher boiling points
Are more viscous (flow less easily

Question 16

Blast Furnace: CO2 +C –> 2CO

Answer 16

High temperature

Carbon dioxide reduced by carbon to give monoxide

Question 17

Blast Furnace C + O2 –> CO2

Answer 17

Coke is impure carbon
Burns in hot air blast to form carbon dioxide
Strongly exothermic

Question 18

Blast Furnace: Fe2O3 + 3CO –> 2Fe + 3CO2

Answer 18

Carbon monoxide, main reducing agent-iron oxide

Iron melts & flows to bottom of the furnace, tapped

Question 19

Blast furnace: Fe2O3 + 3C –> 2Fe + 3CO

Answer 19

In hotter parts of furnace
Some iron oxide also reduced by carbon
Carbon monoxide, not dioxide, made at these temperatures

Question 20

Blast furnace: CaCO3 –> CaO + CO2

Answer 20

Limestone added to furnace
Removes impurities
Limestone undergoes thermal decomposition
Endothermic - if too much limestone added furnace is cooled

Question 21

Blast furnace: CaO + SiO2 –> CaSiO3

Answer 21

To remove impurities
Reacts with silicon dioxide to make calcium silicate
Trickles to bottom of furnace as molten slag, which floats on top of molten iron & can be tapped off separately