1. Extraction of Metals

2. GENERAL PRINCIPLES
General principles
ores of some metals are very common (iron, aluminium)
others occur only in limited quantities in selected areas
high grade ores are cheaper to process because,
ores need to be purified before being reduced to the metal

3. GENERAL PRINCIPLES
General principles
The method used to extract metals depends on the . . .
• purity required
• energy requirements
• cost of the reducing agent
• position of the metal in the reactivity series

4. Reactivity Series K Na Ca Mg Al C Zn Fe H Cu Ag
• lists metals in descending reactivity
• hydrogen and carbon are often added
• the more reactive a metal the less likely it will be found in its pure, or native, state
• consequently, it will be harder to convert it back to the metal.

5. Reactivity Series Low in series occur native or
Cu, Ag extracted by roasting an ore
Middle of series metals below carbon are extracted by reduction
Zn, Fe of the oxide with carbon or carbon monoxide
High in series reactive metals are extracted using electrolysis
Na, Al - an expensive method due to energy costs
Variations can occur due to special properties of the metal.

6. Specific methods to learn
• reduction of metal oxides with carbon IRON
• reduction of metal halides with a metal TITANIUM
• reduction of metal oxides by electrolysis ALUMINIUM
• reduction of metal oxides with a metal CHROMIUM

7. IRON

8. EXTRACTION OF IRON high temperature process continuous
Occurs in the BLAST FURNACE
high temperature process
continuous
iron ores are REDUCED by carbon / carbon monoxide
is possible because iron is below carbon in the reactivity series

9. RAW MATERIALS HAEMATITE - Fe2O3 a source of iron
COKE fuel / reducing agent
CHEAP AND PLENTIFUL
LIMESTONE conversion of silica into slag
(calcium silicate) – USED IN THE
CONSTRUCTION INDUSTRY
AIR source of oxygen for combustion

10. G A C D B B E F THE BLAST FURNACE
IN THE BLAST FURNACE IRON ORE IS REDUCED TO IRON.
THE REACTION IS POSSIBLE BECAUSE CARBON IS ABOVE IRON IN THE REACTIVITY SERIES
Click on the letters to see what is taking place A C D B B E F

11. COKE, LIMESTONE AND IRON ORE ARE ADDED AT THE TOP
THE BLAST FURNACE
COKE, LIMESTONE AND IRON ORE ARE ADDED AT THE TOP
Now move the cursor away from the tower A

12. HOT AIR IS BLOWN IN NEAR THE BOTTOM
THE BLAST FURNACE
HOT AIR IS BLOWN IN NEAR THE BOTTOM
OXYGEN IN THE AIR REACTS WITH CARBON IN THE COKE. THE REACTION IS HIGHLY EXOTHERMIC AND GIVES OUT HEAT.
CARBON + OXYGEN CARBON + HEAT
DIOXIDE
C O CO2 B B
Now move the cursor away from the tower

13. THE BLAST FURNACE
THE CARBON DIOXIDE PRODUCED REACTS WITH MORE CARBON TO PRODUCE CARBON MONOXIDE C
Now move the cursor away from the tower
CARBON CARBON CARBON
DIOXIDE MONOXIDE
C + CO CO

14. THE CARBON MONOXIDE REDUCES THE IRON OXIDE
THE BLAST FURNACE
THE CARBON MONOXIDE REDUCES THE IRON OXIDE
CARBON IRON CARBON + IRON
MONOXIDE OXIDE DIOXIDE
3CO + Fe2O CO Fe D
Now move the cursor away from the tower

15. CALCIUM SILICATE (SLAG) IS PRODUCED MOLTEN SLAG IS RUN OFF AND COOLED
THE BLAST FURNACE
SILICA IN THE IRON ORE IS REMOVED BY REACTING WITH LIME PRODUCED FROM THE THERMAL DECOMPOSITION OF LIMESTONE
CALCIUM SILICATE (SLAG) IS PRODUCED
MOLTEN SLAG IS RUN OFF AND COOLED
CaCO3 CaO + CO2
CaO + SiO CaSiO3 E
Now move the cursor away from the tower

16. F THE BLAST FURNACE MOLTEN IRON RUNS TO THE BOTTOM OF THE FURNACE.
IT IS TAKEN OUT (CAST) AT REGULAR INTERVALS
CAST IRON
- cheap and easily moulded
- used for drainpipes, engine blocks F
Now move the cursor away from the tower

17. HOT WASTE GASES ARE RECYCLED TO AVOID POLLUTION AND SAVE ENERGY
THE BLAST FURNACE G
HOT WASTE GASES ARE RECYCLED TO AVOID POLLUTION AND SAVE ENERGY
CARBON MONOXIDE - POISONOUS
SULPHUR DIOXIDE - ACIDIC RAIN
CARBON DIOXIDE - GREENHOUSE GAS
RECAP

18. Waste gases and pollution
SULPHUR DIOXIDE
• sulfur is found in the coke; sulfides occur in the iron ore
• burning sulfur and sulfides S O2 ——> SO2
produces sulfur dioxide
• sulfur dioxide gives SO H2O ——> H2SO3
rise to acid rain sulfurous acid
CARBON DIOXIDE
• burning fossil fuels increases the amount of this greenhouse gas

19. Limitations of carbon reduction
Theoretically, several other important metals can be extracted this way but are not because they combine with the carbon to form a carbide
e.g. Molybdenum, Titanium, Vanadium, Tungsten

20. Exam Questions – Q7a
Q7. This question is about the extraction of metals.
(a) Coke is mainly carbon and is a raw material used in the extraction of iron from iron(III)
oxide.
(i) Write an equation for the formation of carbon monoxide from carbon.
(1)
(ii) Write an equation for the reduction of iron(III) oxide to iron by carbon monoxide.
(iii) The Earth’s resources of iron(III) oxide are very large and commercial ores have a
high iron content. Give one economic and one environmental reason for recycling
scrap iron and steel.
Economic reason
Environmental reason
(2)

21. Q7 Answer M7. (a) (i) 2C + O2 → 2CO OR C + CO2 → 2CO 1
(iii) Economic:
• Scrap iron/steel has higher iron content.
• Recycling involves lower energy
consumption
• Blast furnace not required
Ignore cost 1
Environmental:
• Reduces greenhouse gas / CO2/ SO2
emission.
• Reduces acid rain
• Reduces mining
• Reduces landfill
• Removes an eyesore
M7. (a) (i) 2C + O2 → 2CO OR
C + CO2 → 2CO 1
(ii) Fe2O3 + 3CO → 2Fe + 3CO2 1

22. Exam Questions – Q9 a and b
Iron is extracted from iron(III) oxide in a continuous process, whereas titanium is extracted
from titanium(IV) oxide in a batch process.
(a) Suggest why a high-temperature batch process is less energy-efficient than a high temperature continuous process.
(2)
(b) Write an overall equation for the reduction of iron(III) oxide in the Blast Furnace.

23. Q9 Answer M9. (a) Batch process involves stopping and starting (1)
Energy lost when cools down after stopping or energy needed to heat up each time (1)
(b) Fe2O3+ 3C → 2Fe + 3CO use of C or CO (1)
balance (1)
or Fe2O3 + 3CO → 2Fe + 3CO2
or 2Fe2O3+ 3C → 4Fe + 3CO2

24. Exam Questions – Q12 a
Q12. (a) When iron(III) oxide is reduced in the Blast Furnace, both carbon and carbon
monoxide act as reducing agents.
(i) Write an equation to illustrate how carbon monoxide is formed in the Blast Furnace.
(ii) Write an equation to illustrate how carbon monoxide reduces iron(III) oxide.
(iii) Suggest in terms of collisions why, in the Blast Furnace, carbon monoxide reacts
more rapidly with iron(III) oxide than does carbon.
(4)

25. Answer Q12 M12. (a) (i) C + CO2 → 2CO
(or 2C + O2 → 2CO, or carbon reduction of an iron oxide) 1
(ii) 3CO + Fe2O3 →3CO2 + 2Fe
(iii) CO is gaseous (or C is solid)
CO has more collisions (or C has very few collisions)

26. Exam Questions –Q15 a
Q15. (a) Iron is extracted in a Blast Furnace by a continuous reduction process. Identify two
reducing agents present in the Blast Furnace. In each case, write an equation to show
how the reducing agent reacts in the formation of iron.
Reducing agent
Equation
Reducing agent

27. Answer Q15 Reducing agent 1: C(1) (or coke) Not coal
Equation: 3C + Fe2O3 → 3CO + 2Fe (1)
or + 2Fe2O3 → 3CO2+ 4Fe
C + O2 → CO2
C + ½ O2 →CO
CO2 + C → 2CO
penalise Fe2 (allow Fe3O4 and FeO)
Reducing agent 2: CO (1)
Equation: 3CO + Fe2O3 → 3CO2+ 2Fe (1)
(again allow Fe3O4, FeO)
Equation mark depends on correct reducing agent

28. TITANIUM

29. Titanium extraction TiO2 (s) + 3C (s) TiC (s) + 2CO (g)
• titanium ores (titanium(IV) oxide - TiO2) are very common
• titanium however is not used extensively as its extraction is
difficult using conventional methods
• the oxide can be reduced by carbon but the titanium produced
reacts with the carbon to give titanium carbide
TiO2 (s) + 3C (s) TiC (s) + 2CO (g)
• the extraction is a batch process so there is much time wasted
and heat lost; this makes it even more expensive

30. The titanium oxide is first converted to titanium chloride by heating it with carbon in a stream of chlorine gas
TiO2(s) C(s) Cl2(g) ——> TiCl4(l) CO(g)
The titanium chloride is then purified using fractional distillation under an inert atmosphere of argon or nitrogen
The titanium chloride is then reduced in a furnace using either sodium or magnesium
TiCl4(l) Na(s) ——> Ti(s) NaCl(s)
TiCl4(l) Mg(s) ——> Ti(s) MgCl(s)
The reduction of TiCl4 is carried out in an atmosphere of argon because the titanium reacts with oxygen at high temperatures.

31. Exam Questions – Q1 Q1. Metals can be extracted by different methods.
(a) Give one reason why titanium cannot be extracted directly from titanium(IV) oxide using carbon.
(1)
(b) Titanium steel is an alloy of titanium and iron. Titanium steel is extracted from the mineral ilmenite (FeTiO3) in a two-stage process.
Purified FeTiO3 is first converted into a mixture of two metal chlorides. These two metal chlorides are then reduced simultaneously using sodium.
(i) Write an equation for the reaction of FeTiO3 with chlorine and carbon to produce iron(III) chloride (FeCl3), titanium(IV) chloride and carbon monoxide.
(ii) Write an equation for the simultaneous reduction of the mixture of iron(III) chloride
and titanium(IV) chloride to iron and titanium using sodium.

32. Answer Q1 M1. (a) Ti is not produced OR
TiC / carbide is produced OR titanium reacts with carbon
Product is brittle
(b) (i) FeTiO3+ 3½Cl2+ 3C FeCl3+ TiCl4+ 3CO
(ii) FeCl3+ TiCl4 + 7Na NaCl + Fe + Ti
2FeCl3+ TiCl4 + 10Na NaCl + 2Fe + Ti
Ignore state symbols
Credit multiples including

33. Exam Question – 5d
5(d) Magnesium is used in the extraction of titanium.
(i) Write an equation for the conversion of titanium(IV) oxide into titanium(IV) chloride.
(2)
(ii) Write an equation for the extraction of titanium from titanium(IV) chloride using
magnesium.
(1)
(iii) State the role of magnesium in this extraction.

34. Answer 5d (ii) TiCl4+ 2Mg Ti + 2MgCl2 Or multiples
(d) (i) M1 use of Cl2 and C
M2 balanced equation consequential on correct reactants
TiO2+ 2Cl2+ 2C TiCl4+ 2CO OR
TiO2 + 2Cl2 + C TiCl4 + CO2
(ii) TiCl4+ 2Mg Ti + 2MgCl2
Or multiples
Ignore state symbols 1
(iii) Reducing agent OR reduces TiCl4 OR
Electron donor
Credit “reduction” or “reductant”
Penalise “electron pair donor”

35. Exam Question – 7b
7(b) Pure titanium is extracted by the reduction of titanium(IV) chloride, but not by the direct reduction of titanium(IV) oxide using carbon.
(i) Write an equation for the conversion of titanium(IV) oxide into titanium(IV) chloride.
(2)
(ii) Write an equation for the extraction of titanium from titanium(IV) chloride.
(iii) State why titanium is not extracted directly from titanium(IV) oxide using carbon.
(1)

36. Answer 7b (b) (i) M1 Use of Cl2 and C
M2 Balanced equation consequential on correct reactants
EITHER
TiO2+ 2Cl2+ 2C → TiCl4 + 2CO OR
TiO2 + 2Cl2 + C → TiCl4 + CO2
(ii) M1 Use of Na OR Mg
TiCl4+ 4Na → Ti + 4NaCl
TiCl4 + 2Mg → Ti + 2MgCl2
(iii) One from
• TiC / carbide is produced
• Product is brittle
• Product is a poor engineering material

37. Exam Question – 11c
11(c) Identify a reducing agent used to obtain titanium metal from titanium(IV) chloride. In addition to a high temperature, state a condition that is used for this reaction and explain why this condition is necessary.
Reducing agent
Condition
Explanation

38. Answer 11c (c) Na (or Mg); Argon;
Na (or Mg or TiCl4) reacts with air (or oxygen or water)
( or impurities of O or N in Ti);

39. Exam Question – 18b
18 (b) (i) State why carbon cannot be used to reduce titanium(IV) oxide directly to titanium.
(ii) Carbon is used in one of the steps in the batch process for titanium extraction. Write
an equation for the reaction which occurs in this step and state a condition under
which this reaction is carried out.
Equation
Condition
(4)

40. Answer 18b (b) (i) (Titanium) carbide is formed (1)
Allow C bonds / reacts with Ti
ii) Equation: TiO2+ 2C (or C) + 2Cl2 → TiCl4+ 2CO (or CO2) (1)
(1) All species correct
(1) Balanced equation
Condition: High temperature (1) or (700 – 1100°C)
NOT “heat”
Mark independently

41. ALUMINIUM

42. Extraction of aluminium
Aluminium is above carbon in the series so it cannot be extracted from its ores in the same way as carbon.
Electrolysis of molten aluminium ore (alumina) must be used
As energy is required to melt the alumina and electrolyse it, a large amount of energy is required.

43. Raw Materials
BAUXITE aluminium ore
Bauxite contains alumina (Al2O3 aluminium oxide) plus impurities such as iron oxide – it is purified before use.

44. Raw Materials
BAUXITE aluminium ore
Bauxite contains alumina (Al2O3 aluminium oxide) plus impurities such as iron oxide – it is purified before use.
CRYOLITE Aluminium oxide has a very
high melting point.
Adding cryolite lowers the melting point and saves energy.

45. Electrolysis Unlike iron, aluminium cannot be extracted using carbon.
(Aluminium is above carbon in the reactivity series)

46. Electroylsis Unlike iron, aluminium cannot be extracted using carbon.
(Aluminium is above carbon in the reactivity series)
Reactive metals are extracted using electrolysis

47. Electroylsis Unlike iron, aluminium cannot be extracted using carbon.
(Aluminium is above carbon in the reactivity series)
Reactive metals are extracted using electrolysis
Electrolysis is expensive - it requires a lot of energy…
- ore must be molten (have high melting points)
- electricity is needed for the electrolysis process

48. Electrolysis THIS IS BECAUSE THE IONS ARE NOT FREE TO MOVE
SOLID IONIC COMPOUNDS DON’T CONDUCT ELECTRICITY
THIS IS BECAUSE THE IONS ARE NOT FREE TO MOVE

49. THIS IS BECAUSE THE IONS ARE NOT FREE TO MOVE
SOLID IONIC COMPOUNDS DON’T CONDUCT ELECTRICITY
THIS IS BECAUSE THE IONS ARE NOT FREE TO MOVE
DISSOLVING IN WATER or… MELTING
ALLOWS THE IONS TO MOVE FREELY

50. THIS IS BECAUSE THE IONS ARE NOT FREE TO MOVE
SOLID IONIC COMPOUNDS DON’T CONDUCT ELECTRICITY
THIS IS BECAUSE THE IONS ARE NOT FREE TO MOVE
DISSOLVING IN WATER or… MELTING
ALLOWS THE IONS TO MOVE FREELY
POSITIVE IONS MOVE TO THE NEGATIVE ELECTRODE
NEGATIVE IONS MOVE TO THE POSITIVE ELECTRODE

51. EXTRACTION OF ALUMINIUM

52. EXTRACTION OF ALUMINIUM
CARBON ANODE
THE CELL CONSISTS OF A CARBON ANODE

53. EXTRACTION OF ALUMINIUM
STEEL CATHODE
CARBON LINING
THE CELL CONSISTS OF A CARBON LINED STEEL CATHODE

54. EXTRACTION OF ALUMINIUM
MOLTEN ALUMINA and CRYOLITE
ALUMINA IS DISSOLVED IN MOLTEN CRYOLITE Na3AlF6
SAVES ENERGY - the mixture melts at a lower temperature

55. EXTRACTION OF ALUMINIUM
MOLTEN ALUMINA and CRYOLITE
ALUMINA IS DISSOLVED IN MOLTEN CRYOLITE Na3AlF6
aluminium and oxide ions are now free to move

56. Al3+ + 3e- Al EXTRACTION OF ALUMINIUM
POSITIVE ALUMINIUM IONS ARE ATTRACTED TO THE NEGATIVE CATHODE
CARBON CATHODE
Al e- Al
EACH ION PICKS UP 3 ELECTRONS AND IS DISCHARGED

57. 2 O2- O2 + 2e- EXTRACTION OF ALUMINIUM
NEGATIVE OXIDE IONS ARE ATTRACTED TO THE POSITIVE ANODE
CARBON ANODE
2 O O e-
EACH ION GIVES UP 2 ELECTRONS AND IS DISCHARGED

58. EXTRACTION OF ALUMINIUM
ELECTRONS
CARBON ANODE
CARBON CATHODE

59. EXTRACTION OF ALUMINIUM
ELECTRONS
OXIDATION (LOSS OF ELECTRONS) TAKES PLACE AT THE ANODE
CARBON ANODE
ANODE O O e- OXIDATION

60. EXTRACTION OF ALUMINIUM
ELECTRONS
OXIDATION (LOSS OF ELECTRONS) TAKES PLACE AT THE ANODE
REDUCTION (GAIN OF ELECTRONS) TAKES PLACE AT THE CATHODE
CARBON CATHODE
ANODE O ½O e- OXIDATION
CATHODE Al e Al REDUCTION

61. EXTRACTION OF ALUMINIUM
ELECTRONS
OXIDATION (LOSS OF ELECTRONS) TAKES PLACE AT THE ANODE
CARBON ANODE
REDUCTION (GAIN OF ELECTRONS) TAKES PLACE AT THE CATHODE
CARBON CATHODE
ANODE O O e- OXIDATION
CATHODE Al e Al REDUCTION

62. PROBLEM EXTRACTION OF ALUMINIUM
CARBON DIOXIDE
PROBLEM
THE CARBON ANODES REACT WITH THE OXYGEN TO PRODUCE CARBON DIOXIDE
CARBON ANODE

63. PROBLEM EXTRACTION OF ALUMINIUM
CARBON DIOXIDE
PROBLEM
THE CARBON ANODES REACT WITH THE OXYGEN TO PRODUCE CARBON DIOXIDE
CARBON ANODE
THE ANODES HAVE TO BE REPLACED AT REGULAR INTERVALS, THUS ADDING TO THE COST OF THE EXTRACTION PROCESS

64. Properties of aluminium
ALUMINIUM IS NOT AS REACTIVE AS ITS POSITION
IN THE REACTIVITY SERIES SUGGESTS
THIS IS BECAUSE A THIN LAYER OF ALUMINIUM OXIDE QUICKLY FORMS ON ITS SURFACE AND PREVENTS FURTHER REACTION TAKING PLACE
THIN LAYER OF OXIDE
ANODISING PUTS ON A CONTROLLED LAYER SO THAT THE METAL CAN BE USED FOR HOUSEHOLD ITEMS SUCH AS PANS AND ELECTRICAL GOODS

65. Exam Question – 7C
7(c) Aluminium is extracted by the electrolysis of a molten mixture containing aluminium oxide.
(i) State why the electrolysis needs to be of a molten mixture.
(1)
(ii) Write an equation for the reaction of oxide ions at the positive electrode during the
electrolysis.
(iii) State why the positive electrodes need frequent replacement.
(iv) Give the major reason why it is less expensive to recycle aluminium than to extract it
from aluminium oxide by electrolysis.

66. Answer 7C (c) (i) One from To allow • ions to move • current to flow
• it to conduct electricity
(ii) 2O2– → O2 + 4e–
(iii) Carbon / graphite / the electrodes oxidise OR
Carbon / graphite / the electrodes burn in / react with the oxygen
formed
carbon dioxide / CO2 is formed
(iv) Recycling involves lower electricity OR less energy
consumption
The converse for electrolysis
Ignore references to raw materials
The answer MUST show some evidence of comparison e.g. lower
or less

67. Exam Question – 11D
11(d) (i) State two essential conditions used for the electrolytic extraction of aluminium from
aluminium oxide.
Condition
Condition
(ii) Write an equation to illustrate how aluminium is formed from aluminium ions in this
process.
(3)

68. Answer 11D (d) (i) cryolite; 1 Molten (or liquid or solution);
(ii) Al3+ + 3e– → Al;

69. CHROMIUM

70. Extraction of Chromium
The method of extraction often depends on the purity required.
IMPURE CHROMIUM
The ore (chromite) is reduced by heating with carbon. ...
FeCr2O4(s) C(s) ——> Fe(s) Cr(s) CO(g)

71. Extraction of Chromium
PURE CHROMIUM
The chromite is converted to chromium(III) oxide which is then reduced using aluminium at high temperatures. This is known as ACTIVE METAL REDUCTION.
Cr2O3(s) Al(s) ——> 2Cr(s) Al2O3(s)

72. Other Extractions needed

73. Tungsten The extraction of tungsten is carried out using Hydrogen
It is expensive and explosive
WO3 (s) + 3H2 (g) W (s) + 3H2O (l)

74. Sulfide Ores Lead Sulfide and Zinc sulfide
Roast the sulfide in air to turn it into an oxide
2Zn (s) + 3O2 (g) ZnO (s) + 2SO2 (g)
Bad – Releases sulfur dioxide (acid rain)
Good – Can convert it into sulfuric acid
The oxide can then be reduced to the metal

75. Molybdenum extraction
1st stage is to roast the ore in the air to remove sulfur
MoS2 + 3 ½ O MoO3 + 2SO2
Pure molybdenum is then reduced using hydrogen
MoO3 + 3H Mo + 3H2O

76. Other reductions that come up regularly in CHEM 2
Iron (III) oxide
2Fe2O3 + 3C Fe + 3CO2
Fe2O3 + 3CO Fe + 3CO2
Manganese dioxide (manganese (IV) oxide)
MnO2 + C Mn + CO2
MnO2 + 2CO Mn + 2CO2

77. Copper carbonate heat directly with carbon 2CuCO3 + C 2Cu + 3CO2 Or
Heat until it decomposes then reduce the oxide with carbon
CuCO CuO + CO2
Then
2CuO + C Cu + CO2

78. Scrap iron and copper extraction
Works with a low grade ore in solution
Acidified water dissolves the copper compounds in the ore
Scrap iron is added, the iron dissolves and reduces the copper (II) ions. The copper then precipitates out of the solution
Slower and only a low yield produced but it is cheaper and it doesn’t need a high temp or produce CO2
Cu2+ (aq) + Fe (s) Cu (s) + Fe 2+ (aq)

79. (c) Scrap iron is used to extract copper from dilute aqueous solutions containing copper(II) ions.
Explain, in terms of redox, what happens to the copper(II) ions in this extraction.
Either order
Penalise reference to incorrect number of electrons in M1
M1 The Cu2+ / copper(II) ions / they have gained (two) electrons
OR Cu2+ + 2e– Cu
For M1, accept “copper” if supported by correct half-equation or
simplest ionic equation
OR oxidation state / number decreases (or specified from 2 to 0)
Ignore charge on the electron
M2 The Cu2+ / copper(II) ions / they have been reduced
For M2 do not accept “copper” alone 2

80. Extraction of magnesium in sea water
React Mg ions with hydroxide ions to form magnesium hydroxide
Mg2+ + 2OH Mg(OH)2
Next react with HCl to give magnesium chloride
Mg(OH)2 + 2HCl MgCl2 + 2H2O
Final step MgCl2 is electrolysed to form magnesium and chlorine

81. Recycling Problems • high cost of collection and sorting
• unsightly plant
• high energy process
Benefits • less visible pollution of environment by waste
• provides employment
• reduces the amount of new mining required
• maintains the use of valuable resources
• strategic resources can be left underground