Question

Explain why aluminum, magnesium, and sodium metals are obtained by electrolysis instead of by reduction with chemical reducing agents.

Short answer

Aluminum, magnesium, and sodium metals are obtained by electrolysis instead of by reduction with chemical reducing agents due to their high reactivity and position in the reactivity series. Their strong affinity for oxygen makes direct reduction with chemical reducing agents difficult. Electrolysis allows for the extraction of these metals in a pure form from their respective compounds, such as aluminum from bauxite, magnesium from magnesite or seawater, and sodium from sodium chloride.

Step-by-step solution

Understanding the reactivity series

The reactivity series is a ranking of metals in order of their reactivity, with very reactive metals at the top and less reactive metals at the bottom. It is an essential concept in chemistry and helps us understand which extraction methods are suitable for different metals. Metals above hydrogen in the reactivity series are typically extracted by electrolysis, while metals below hydrogen are extracted by reduction using chemical reducing agents.

Discussing the properties of aluminum

Aluminum is a highly reactive metal and is found in the Earth's crust as an ore called bauxite. The bauxite ore contains aluminum oxide (Al2O3), which needs to be extracted and purified to obtain aluminum metal. Aluminum has a high affinity for oxygen, making it difficult to reduce directly with a chemical reducing agent like carbon. Therefore, aluminum is extracted through electrolysis, specifically the Hall-Héroult process, which allows for the extraction of pure aluminum metal from its oxide.

Discussing the properties of magnesium

Magnesium is another highly reactive metal. Magnesium is commonly found as an ore called magnesite (MgCO3) or in seawater as magnesium chloride (MgCl2). Similar to aluminum, magnesium has a strong affinity for oxygen and is not easily reduced by chemical reducing agents. Magnesium is produced using electrolysis, specifically the Dow Process or the electrolysis of magnesium chloride from seawater. The electrolysis process allows for the extraction of pure magnesium metal from its compound.

Discussing the properties of sodium

Sodium is a very reactive metal and is usually found in the form of sodium chloride (NaCl), which is the main component of table salt. As a highly reactive metal, sodium cannot be easily reduced by chemical reducing agents. Instead, sodium is extracted using electrolysis in a process known as the Down's Process. In this process, molten sodium chloride is electrolysed to produce sodium metal and chlorine gas. This allows for the extraction of pure sodium metal from its compound.

Conclusion

In summary, aluminum, magnesium, and sodium metals are obtained by electrolysis instead of by reduction with chemical reducing agents due to their high reactivity and position in the reactivity series. These metals have a strong affinity for oxygen, which makes direct reduction with chemical reducing agents difficult. Electrolysis allows for the extraction of these metals in a pure form from their respective compounds.