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Can you think of some uses for aluminium?

Iron nipples

Last lesson

• The extraction of aluminium from aluminium oxide (Bauxite)

Reactivity Series

Electrolysis of aluminium oxide

CO2

Electrolysis of aluminium oxide

Aluminium oxide has a high melting point (2054°C) (EXPENSIVE)

Electrolysis of aluminium oxide

Aluminium oxide will dissolve in molten cryolite which melts at “only” 959°C (CHEAPER)

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.

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).

Electrolysis of aluminium oxide

At the cathode the aluminium ions gain electrons and become aluminium atoms.

4Al3+ + 12e- 4Al

Electrolysis of aluminium oxide

At the anodes the oxygen ions lose electrons and become oxygen atoms.

6O2- 3O2 + 12e-

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.

Electrolysis of aluminium oxide

Molten aluminium is tapped from the bottom of the chamber

Electrolysis of aluminium oxide

This all requires LOTS of electricity so is an expensive process.

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

A sheet!

Today’s lesson

• Extraction of Zinc using electrolysis and by heating with carbon

• Extraction of Chromium using the thermite process

Zinc

Zinc blende

I’m mainly Zinc Sulphide ZnS (s)

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)

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)

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!

Another way of separating the zinc in zinc oxide

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)

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)

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!

Extraction of chromium

Extraction of chromium

• Another “Thermite” reaction

Cr2O3(s) + 2Al(s) Al2O3(s) + 2Cr(s)

YouTube - New Improved Chromium thermite

Extraction of chromium

• Another “Thermite” reaction

Cr2O3(s) + 2Al(s) Al2O3(s) + 2Cr(s)

YouTube - New Improved Chromium thermite

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Moles!