11 Metal Extraction

State 2 reasons why carbon is often used to extract metals from their oxides?

-Cheap -Abundant

Examples of metal alloys

Aluminium Steel Gold Brass Bronze

Alloys

An alloy is a combination of 2+ elements, where at least 1 is a metal. The ions of the different elements are different sizes. This makes it harder for the layers to slide across each other when a force is applied to the alloy. This makes alloys stronger than pure metals, and so they are often used in construction.

The following question concerns the production of aluminium from its ore, bauxite, using electrolysis. Bauxite is purified to aluminium oxide (Al2O3) which is then subjected to electrolysis to produce pure aluminium.

Cathode The cathode is the negative electrode. This is where reduction occurs: Al3+(l) + 3e- → Al(s) Anode The anode is the positive electrode. This is where oxidation occurs.2O2-(l) → O2(g) + 4e-

Extracting metals using electrolysis

Electrolysis is used to extract metals such as aluminium, which are higher in the reactivity series than carbon. Powdered aluminium ore (Al2O3) is first mixed with another aluminium salt called cryolite. This mixture has a lower melting point than pure Al2O3. This makes it cheaper as less energy is needed to melt the powder. Once molten, a large voltage is applied. The aluminium is formed at the cathode Oxygen forms at the carbon anode. The carbon and oxygen react to give carbon dioxide. The anode is usually made of carbon because it is a good conductor.

How is carbon used to extract metals?

In the reduction, the metal oxide loses oxygen to form a pure metal. Reduction with carbon normally involves heating the metal oxide in the presence of the carbon, which is often used in the form of coal.

What are the disadvantages of extracting meetals using electrolysis?

Lots of energy is needed to: -Melt the solid ionic compound to allow the ions to flow -Produce the electrical current. This costs a lot of money.

Extraction of metals

Most metals are only found as compounds because the metal has reacted with other elements in the past. Because of this, the metal has to be extracted from the ore where the metal is found.

Why is carbon used to extract metals?

Reducing a metal with carbon will result in the extraction of the metal if the metal is lower in the reactivity series than carbon. Carbon is used because it is cheap and abundant.