5.4 describe and explain the main reactions involved in the extraction of iron from iron ore (haematite), using coke, limestone and air in a blast furnace

Extraction of iron

5.3 write ionic half-equations for the reactions at the electrodes in aluminium extraction

Half equations

The reaction at the negative electrode (cathode) for aluminium extraction is:

Al3- + 3e----> Al

The reaction at the positive electrode (anode) for aluminium extraction is:

2O2- ----> O2 + 4e

5.2 describe and explain the extraction of aluminium from purified aluminium oxide by electrolysis, including: i the use of molten cryolite as a solvent and to decrease the required operating temperature ii the need to replace the positive electrodes iii the cost of the electricity as a major factor

Aluminium oxide has a very high melting point and hence it is dissolved in molten cryolite to make the electrolyte. This mixture has a much lower melting point and is also better conductor of electricity than molten aluminium oxide.

The electrodes are made of graphite (carbon) and they need to be replaced regularly because of the hot temperatures and the carbon anodes burn with oxygen to create carbon dioxide. This means that they need to be replaced regularly and this adds to the cost of the extraction.

Large amounts of energy are needed to produce aluminium, this is why using molten cryolite saves quite a lot of money, as it has a reasonably low melting point and acts as a solvent for aluminium oxide.

5.1 explain how the methods of extraction of the metals in this section are related to their positions in the reactivity series

Methods of extraction

The metal of extraction is linked to the position of the metal in the reactivity series, since the more reactive metals are better at 'keeping hold' if the elements in their compounds. This means the more reactive the metal, the more difficult and expensive it is to extract.

4.25 predict the effects of changing the pressure and temperature on the equilibrium position in reversible reactions.

By changing the pressure and temperature it is possible to shift the position of the equilibrium of the reaction.

4.24 understand the concept of dynamic equilibrium

Dynamic equilibrium

Dynamic equilibrium is when a reversible reaction is happening both ways at the same time, at the same rate.

4.23 describe reversible reactions such as the dehydration of hydrated copper(II) sulfate and the effect of heat on ammonium chloride

Adding water to copper (II) sulfate, makes it hydrated.

If you remove water from the hydrated copper (II) sulfate, it becomes dehydrated.