Reduction of Metals (Extraction from Ore)

There are 3 main methods of extracting metals from their ore.

They are reduction of the ore with carbon, reduction of the molten ore by electrolysis, and reduction of the ore with a more reactive metal.

Extraction using carbon

Metals such as zinc, iron and copper are present in ores as their oxides. Each of these oxides is heated with carbon to obtain the metal.

The metal oxide loses oxygen, and is therefore reduced. The carbon gains oxygen, and is therefore oxidised.

Electrolysis

Ionic substances can be broken down into the elements they are made from by electricity, in a process called electrolysis.

For electrolysis to work, the ions must be free to move. When an ionic compound is dissolved in water, or melts the ions break free from the ionic lattice. These ions are then free to move. The solution or molten ionic compound is called an electrolyte.

During electrolysis:

• Positively charged ions move to the negative electrode. Metal ions are positively charged, so metals are produced at the negative electrode (cathode).

• Negatively charged ions move to the positive electrode. Non-metal ions, such as oxide ions and chloride ions, are negatively charged, so gases such as oxygen or chlorine are produced at the positive electrode (anode).

Reduction of metal halides with metals

In many cases, carbon cannot be used to reduce the metal oxide to the metal as the metal reacts with carbon to form the carbide instead.

It is possible to avoid this problem by first converting the ore to the chloride, and then reducing the chloride with a more reactive metal such as magnesium or sodium. This is the method used to extract titanium.

This video recaps all 3 methods (extraction using carbon, electrolysis and using a more reactive metal):