Aluminium is extracted from its ore (bauxite) using the electrolysis process. Here are the steps:

1. **Purification**: Bauxite contains aluminium oxide (Al2O3). Before the electrolysis process, it is purified using the Bayer process, where it is mixed with hot sodium hydroxide which dissolves the aluminium oxide. The impurities are left behind and the solution is then cooled, causing the aluminium oxide to precipitate out. This is then heated to a very high temperature to leave pure aluminium oxide.

2. **Electrolysis**: The purified aluminium oxide is dissolved in molten cryolite. Cryolite is a compound of aluminium, sodium, and fluorine. It lowers the melting point of the aluminium oxide, which would otherwise be too high to be practical for electrolysis.

3. **At the electrodes**: The electrolysis takes place in a steel container lined with graphite. The graphite lining serves as the cathode (negative electrode). The anodes (positive electrodes) are also made of graphite. When electricity is passed through, aluminium ions are reduced at the cathode and oxygen ions are oxidized at the anode.

The half equations are:

At the cathode: Al3+ + 3e- - Al (reduction)

At the anode: 2O2- - 4e- - O2 (oxidation)

4. **Collection of aluminium**: The molten aluminium that forms at the cathode sinks to the bottom of the container, where it is periodically drained off.

5. **Replacement of anodes**: The oxygen produced at the anode reacts with the graphite anodes to produce carbon dioxide, which means the anodes gradually burn away and need to be replaced regularly.

This process is energy-intensive but is the most common method for extracting aluminium due to the high reactivity of the metal, which makes it difficult to extract using other methods.

Question

Aluminium is extracted from its ore (bauxite) using the electrolysis process. Here are the steps:

1. **Purification**: Bauxite contains aluminium oxide (Al2O3). Before the electrolysis process, it is purified using the Bayer process, where it is mixed with hot sodium hydroxide which dissolves the aluminium oxide. The impurities are left behind and the solution is then cooled, causing the aluminium oxide to precipitate out. This is then heated to a very high temperature to leave pure aluminium oxide.

2. **Electrolysis**: The purified aluminium oxide is dissolved in molten cryolite. Cryolite is a compound of aluminium, sodium, and fluorine. It lowers the melting point of the aluminium oxide, which would otherwise be too high to be practical for electrolysis.

3. **At the electrodes**: The electrolysis takes place in a steel container lined with graphite. The graphite lining serves as the cathode (negative electrode). The anodes (positive electrodes) are also made of graphite. When electricity is passed through, aluminium ions are reduced at the cathode and oxygen ions are oxidized at the anode.

The half equations are:

At the cathode: Al3+ + 3e- -> Al (reduction)

At the anode: 2O2- - 4e- -> O2 (oxidation)

4. **Collection of aluminium**: The molten aluminium that forms at the cathode sinks to the bottom of the container, where it is periodically drained off.

5. **Replacement of anodes**: The oxygen produced at the anode reacts with the graphite anodes to produce carbon dioxide, which means the anodes gradually burn away and need to be replaced regularly.

This process is energy-intensive but is the most common method for extracting aluminium due to the high reactivity of the metal, which makes it difficult to extract using other methods.

Knowee AI · Accepted Answer

Aluminium is extracted from its ore (bauxite) using the electrolysis process. Here are the steps:

1. **Purification**: Bauxite contains aluminium oxide (Al2O3). Before the electrolysis process, it is purified using the Bayer process, where it is mixed with hot sodium hydroxide which dissolves the aluminium oxide. The impurities are left behind and the solution is then cooled, causing the aluminium oxide to precipitate out. This is then heated to a very high temperature to leave pure aluminium oxide.

2. **Electrolysis**: The purified aluminium oxide is dissolved in molten cryolite. Cryolite is a compound of aluminium, sodium, and fluorine. It lowers the melting point of the aluminium oxide, which would otherwise be too high to be practical for electrolysis.

3. **At the electrodes**: The electrolysis takes place in a steel container lined with graphite. The graphite lining serves as the cathode (negative electrode). The anodes (positive electrodes) are also made of graphite. When electricity is passed through, aluminium ions are reduced at the cathode and oxygen ions are oxidized at the anode.

The half equations are:

At the cathode: Al3+ + 3e- -> Al (reduction)

At the anode: 2O2- - 4e- -> O2 (oxidation)

4. **Collection of aluminium**: The molten aluminium that forms at the cathode sinks to the bottom of the container, where it is periodically drained off.

5. **Replacement of anodes**: The oxygen produced at the anode reacts with the graphite anodes to produce carbon dioxide, which means the anodes gradually burn away and need to be replaced regularly.

This process is energy-intensive but is the most common method for extracting aluminium due to the high reactivity of the metal, which makes it difficult to extract using other methods.

This question is about electrolysis, extraction of metals, and properties of materials.Describe the process of extracting aluminium from its ore, including the role of cryolite and the reactions at each electrode. Write half equations where appropriate.

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