2.1.gc extraction_of_aluminium.5th F.ppt

2.1.gc extraction_of_aluminium.5th F.ppt

1. ALUMINIUMALUMINIUM

2. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
Aluminium is above carbon in the series so it
cannot be extracted from its ores in the same
way as iron.
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.

3. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
RAW MATERIALSRAW MATERIALS
BAUXITE aluminium ore
Bauxite contains alumina (Al
2
O
3
aluminium oxide) plus
impurities such as iron oxide – it is purified before use.

4. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
RAW MATERIALSRAW MATERIALS
BAUXITE aluminium ore
Bauxite contains alumina (Al
2
O
3
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.

5. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
ELECTROLYSISELECTROLYSIS
Unlike iron, aluminium cannot be extracted using carbon.
(Aluminium is above carbon in the reactivity series)

6. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
ELECTROLYSISELECTROLYSIS
Unlike iron, aluminium cannot be extracted using carbon.
(Aluminium is above carbon in the reactivity series)
Reactive metals are extracted using electrolysis

7. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
ELECTROLYSISELECTROLYSIS
Unlike iron, aluminium cannot be extracted using carbon.
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

8. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
ELECTROLYSISELECTROLYSIS
SOLID IONIC COMPOUNDS DON’T CONDUCT ELECTRICITY
THIS IS BECAUSE THE IONS ARE NOT FREE TO MOVE

9. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
ELECTROLYSISELECTROLYSIS
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

10. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
ELECTROLYSISELECTROLYSIS
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

11. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM

12. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
CARBON ANODE
THE CELL CONSISTS OF A CARBON ANODE

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

14. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
MOLTEN
ALUMINA and
CRYOLITE
ALUMINA IS DISSOLVED IN MOLTEN CRYOLITE Na
3
AlF
6
SAVES ENERGY - the mixture melts at a lower temperature

15. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
MOLTEN
ALUMINA and
CRYOLITE
ALUMINA IS DISSOLVED IN MOLTEN CRYOLITE Na
3
AlF
6
aluminium and oxide ions are now free to move

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

17. O
2-
O + 2e
-

EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
NEGATIVE OXIDE
IONS ARE
ATTRACTED TO
THE POSITIVE
ANODE
EACH ION GIVES UP 2 ELECTRONS AND IS DISCHARGED
CARBON ANODE

18. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
ELECTRONS
CARBON ANODE
CARBON CATHODE

19. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
ELECTRONS
ANODE 3O
2-
1½O
2 + 6e
-
OXIDATION
OXIDATION (LOSS OF
ELECTRONS) TAKES PLACE
AT THE ANODE
CARBON ANODE

20. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
ELECTRONS
CATHODE 2Al
3+
+ 6e
-
2Al REDUCTION
OXIDATION (LOSS OF
ELECTRONS) TAKES PLACE
AT THE ANODE
REDUCTION (GAIN
OF ELECTRONS)
TAKES PLACE AT
THE CATHODE CARBON CATHODE
ANODE 3O
2-
1½O
2 + 6e
-
OXIDATION

21. EXTRACTION OF ALUMINIUMEXTRACTION OF ALUMINIUM
ELECTRONS
OXIDATION (LOSS OF
ELECTRONS) TAKES PLACE
AT THE ANODE
REDUCTION (GAIN
OF ELECTRONS)
TAKES PLACE AT
THE CATHODE
CARBON ANODE
CARBON CATHODE
ANODE 3O
2-
1½O
2 + 6e
-
OXIDATION
CATHODE 2Al
3+
+ 6e
-
2Al REDUCTION

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

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

24. PROPERTIES OF ALUMINIUMPROPERTIES 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