Extraction and use of Metals

Question 1

Electrolysis

Answer 1

• The process of splitting an ionic compound into its component elements using electricity
• Used for the extraction of aluminium
• it takes place the whole year round because electricity is expensive

Question 2

Extraction of aluminium

Answer 2

-Bauxite is the main ore of aluminium
1. Purified aluminium oxide is dissolved into molten cryolite to lower the melting point (decrease required operating temp)
2. For electrolysis to work, the ions need to be separate and free to move(in solids it’s not free so it’s melted )
3. Oxide ions negatively charged so moves to graphite anode(+ electrode)
2O(2-) → O2 + 4e-
4. Aluminium ions positively charged so moves to graphite cathode(- electrode)
Al(3+) + 3e- → Al

Question 3

Why do anodes need to be replaced regularly?

Answer 3

Oxygen reacts with the carbon in graphite to make carbon dioxide and this burns away the electrode

Question 4

Electrons in aluminium extraction

Answer 4

• Aluminium ions gain electrons when they from aluminium atoms
• Oxide ions lose electrons when they from oxygen atoms

Question 5

aluminium extraction diagram

Answer 5

graphite anode (+) at the top
graphite cathode (-) around 
-molten cryolite
-molten aluminium (molten aluminum tapped off)
steel case

Question 6

Uses of aluminium and iron

Answer 6

Aluminium:
-strong and low density- construction of airplanes
-malleable and corrosion resistance- tin foil and drink cans
Iron:
-stainless steel very resistant to corrosion- cutlery

Question 7

The Blast Furnace

Answer 7

1. Haematite, Limestone, Coke(CO2) and air (O2) fed into the blast furnace
2. Carbon reacts with oxygen from air to from carbon dioxide. A lot of heat is released
   (* Oxidised)
   C* + O2 -> CO2
3. Carbon dioxide reacts with more carbon to from carbon monoxide
   CO2 + C* -> 2CO
4. Carbon monoxide reduces Iron oxide to iron.
   Fe ₂ CO₃ + 3CO* -> 2Fe + 3CO ₂
5. Limestone (calcium carbonate) is thermally decomposed to form calcium oxide and carbon dioxide
   (HEAT)
   CaO3 -> CaO + CO2
6. The calcium oxide reacts with silicon dioxide to from slag which is liquid in the furnace
   CaO + SiO2 -> CaSiO3 (calcium silicate)

-Slag can be used for road construction or making concrete.

Question 8

Reduction

Answer 8

Taking oxygen away and giving it to something else.

Question 9

How do methods in extraction relate to position in the reactivity series?

Answer 9

Metals more reactive than carbon is extracted by electrolysis

Metals less reactive than carbon is displaced by carbon/carbon monoxide

Metals less reactive than hydrogen is extracted by various chemical reactions