Do now! Can you think of some uses for aluminium? Iron nipples.
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Transcript of Do now! Can you think of some uses for aluminium? Iron nipples.
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Do now!
Can you think of some uses for aluminium?
Iron nipples
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Last lesson
• The extraction of aluminium from aluminium oxide (Bauxite)
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Reactivity Series
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Electrolysis of aluminium oxide
CO2
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Electrolysis of aluminium oxide
Aluminium oxide has a high melting point (2054°C) (EXPENSIVE)
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Electrolysis of aluminium oxide
Aluminium oxide will dissolve in molten cryolite which melts at “only” 959°C (CHEAPER)
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Electrolysis of aluminium oxide
The molten liquid is put into a large chamber, the walls of which are connected to the negative side of a circuit (cathode). Large positive electrodes (anodes) made of graphite are lowered into the mixture.
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Electrolysis of aluminium oxide
Aluminum oxide is an ionic compound. The positive aluminium ions drift to the negative electrode (cathode) and the negative oxygen ions to the positive electrodes (anodes).
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Electrolysis of aluminium oxide
At the cathode the aluminium ions gain electrons and become aluminium atoms.
4Al3+ + 12e- 4Al
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Electrolysis of aluminium oxide
At the anodes the oxygen ions lose electrons and become oxygen atoms.
6O2- 3O2 + 12e-
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Electrolysis of aluminium oxide
The oxygen immediately reacts with the hot graphite to form carbon dioxide. This means the graphite electrodes have to be replaced occasionally as they wear away.
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Electrolysis of aluminium oxide
Molten aluminium is tapped from the bottom of the chamber
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Electrolysis of aluminium oxide
This all requires LOTS of electricity so is an expensive process.
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Electrolysis of Aluminium• Aluminium oxide has a high melting point (2054°C) (EXPENSIVE)• Aluminium oxide will dissolve in molten cryolite which melts at “only” 959°C
(CHEAPER)• The molten liquid is put into a large chamber, the walls of which are connected to the
negative side of a circuit (cathode). Large positive electrodes (anodes) made of graphite are lowered into the mixture.
• Aluminum oxide is an ionic compound. The positive aluminium ions drift to the negative electrode (cathode) and the negative oxygen ions to the positive electrodes (anodes).
• At the cathode the aluminium ions gain electrons and become aluminium atoms.4Al 3+ + 12e- 4Al
• At the anodes the oxygen ions lose electrons and become oxygen atoms.6O2- 3O2 + 12e-
• The oxygen immediately reacts with the hot graphite to form carbon dioxide. This means the graphite electrodes have to be replaced occasionally as they wear away.
• Molten aluminium is tapped from the bottom of the chamber
Maximum two words per drawing - numbers allowed
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A sheet!
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Today’s lesson
• Extraction of Zinc using electrolysis and by heating with carbon
• Extraction of Chromium using the thermite process
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Zinc
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Zinc blende
I’m mainly Zinc Sulphide ZnS (s)
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Zinc blende
Roasted in air to make zinc oxide
2ZnS(s) + 3O2(g) 2ZnO(s) + 2SO 2(g)
I’m mainly Zinc Sulphide ZnS (s)
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Zinc blende
Roasted in air to make zinc oxide
2ZnS(s) + 3O2(g) 2ZnO(s) + 2SO 2(g)
Zinc oxide reduced by carbon monoxide in a furnace
2ZnO(s) + CO(g) Zn(s) + CO2(g)
I’m mainly Zinc Sulphide ZnS (s)
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Zinc blende
Roasted in air to make zinc oxide
2ZnS(s) + 3O2(g) 2ZnO(s) + 2SO 2(g)
Zinc oxide reduced by carbon monoxide in a furnace
2ZnO(s) + CO(g) Zn(s) + CO2(g)
I’m mainly Zinc Sulphide ZnS (s)
Copy please!
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Another way of separating the zinc in zinc oxide
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Another way of separating the zinc in zinc oxide
React the zinc oxide (a base) with sulphuric acid to make zinc sulphate
H2SO4(aq) + ZnO(s) ZnSO4(aq) + H2O(l)
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Another way of separating the zinc in zinc oxide
React the zinc oxide (a base) with sulphuric acid to make zinc sulphate
H2SO4(aq) + ZnO(s) ZnSO4(aq) + H2O(l)
The solution is then electrolysed giving zinc at the cathode
Zn2+(aq) + 2e- Zn(s)
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Another way of separating the zinc in zinc oxide
React the zinc oxide (a base) with sulphuric acid to make zinc sulphate
H2SO4(aq) + ZnO(s) ZnSO4(aq) + H2O(l)
The solution is then electrolysed giving zinc at the cathode
Zn2+(aq) + 2e- Zn(s)
Copy please!
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Extraction of chromium
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Extraction of chromium
• Another “Thermite” reaction
Cr2O3(s) + 2Al(s) Al2O3(s) + 2Cr(s)
YouTube - New Improved Chromium thermite
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Extraction of chromium
• Another “Thermite” reaction
Cr2O3(s) + 2Al(s) Al2O3(s) + 2Cr(s)
YouTube - New Improved Chromium thermite
You guessed
it!
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Let’s watch something fun
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Moles!