(d) Why are active metals such as Al obtained by electrolysis using molten salts rather than aqueous solutions?

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Understand that active metals like aluminum (Al) are highly reactive and tend to form stable compounds.

Recognize that in aqueous solutions, water is present and can participate in redox reactions.

Consider the electrochemical series: water is more easily reduced than many metal ions, including Al³⁺, meaning water would preferentially undergo reduction to form hydrogen gas instead of reducing Al³⁺ to Al.

Realize that using molten salts allows the metal ions to be reduced without the interference of water, as there is no water present to compete in the reduction process.

Conclude that electrolysis of molten salts provides a more efficient and feasible method to obtain pure active metals like aluminum, as it avoids the side reactions that occur in aqueous solutions.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Electrolysis

Electrolysis is a chemical process that uses electrical energy to drive a non-spontaneous reaction. In this process, an electric current is passed through an electrolyte, causing the decomposition of the compound. This technique is essential for extracting metals from their ores, particularly for active metals that cannot be easily reduced by chemical means.

Molten Salts vs. Aqueous Solutions

Molten salts are ionic compounds that are heated until they become liquid, allowing ions to move freely. In contrast, aqueous solutions contain water as a solvent, which can introduce complications such as competing reactions with water. For active metals like aluminum, using molten salts prevents the formation of hydrogen gas and ensures a more efficient extraction process.

Reactivity of Active Metals

Active metals, such as aluminum, have a strong tendency to lose electrons and form positive ions. This high reactivity makes them difficult to extract using traditional methods, as they readily react with water and other substances. Electrolysis of molten salts allows for the direct reduction of these metals without interference from other reactions, making it a preferred method for their extraction.