Question

The Hall process is an important method by which pure aluminum is prepared from its oxide (alumina, \(\mathrm{Al}_{2} \mathrm{O}_{3}\) ) by indirect reaction with graphite (carbon). Balance the following equation, which is a simplified representation of this process. $$\mathrm{Al}_{2} \mathrm{O}_{3}(s)+\mathrm{C}(s) \rightarrow \mathrm{Al}(s)+\mathrm{CO}_{2}(g)$$

Short answer

The balanced chemical equation for the Hall process is: $$2\mathrm{Al}_{2} \mathrm{O}_{3}(s) + 2\mathrm{C}(s) \rightarrow 4\mathrm{Al}(s) + 3\mathrm{CO}_{2}(g)$$

Step-by-step solution

Write down the given chemical equation

First, let's rewrite the given chemical equation: $$\mathrm{Al}_{2} \mathrm{O}_{3}(s)+\mathrm{C}(s) \rightarrow \mathrm{Al}(s)+\mathrm{CO}_{2}(g)$$

Count the atoms for each element on both sides of the equation

On the left side of the equation, we have: - 2 aluminum (Al) atoms in Al2O3 - 3 oxygen (O) atoms in Al2O3 - 1 carbon (C) atom On the right side of the equation, we have: - 1 aluminum (Al) atom - 1 carbon (C) atom in CO2 - 2 oxygen (O) atoms in CO2

Balance the aluminum atoms

Since there are 2 aluminum atoms on the left side but only 1 on the right side, we can multiply the number of aluminum atoms on the right side by 2: $$\mathrm{Al}_{2} \mathrm{O}_{3}(s)+\mathrm{C}(s) \rightarrow 2\mathrm{Al}(s)+\mathrm{CO}_{2}(g)$$ Now we have: - 2 aluminum (Al) atoms on both sides of the equation

Balance the carbon and oxygen atoms

We now have 2 oxygen (O) atoms on the right side, but there are 3 oxygen atoms on the left side. In order to balance the oxygen atoms, we can multiply the number of CO2 molecules on the right side by 1.5. However, it is better to avoid fractional coefficients in a balanced equation. Therefore, we can balance the equation by multiplying the entire equation by 2: $$2(\mathrm{Al}_{2} \mathrm{O}_{3}(s)+\mathrm{C}(s)) \rightarrow 2(2\mathrm{Al}(s)+1.5\mathrm{CO}_{2}(g))$$ This gives us: $$2\mathrm{Al}_{2} \mathrm{O}_{3}(s) + 2\mathrm{C}(s) \rightarrow 4\mathrm{Al}(s) + 3\mathrm{CO}_{2}(g)$$ Now, all the atoms are balanced on both sides of the equation: - 4 aluminum (Al) atoms - 6 oxygen (O) atoms - 2 carbon (C) atoms The balanced chemical equation for the Hall process is: $$2\mathrm{Al}_{2} \mathrm{O}_{3}(s) + 2\mathrm{C}(s) \rightarrow 4\mathrm{Al}(s) + 3\mathrm{CO}_{2}(g)$$

Key concepts

Hall process

The Hall process, also known as the Hall-Héroult process, is a method used to produce pure aluminum from its oxide form, alumina (\(\text{Al}_2\text{O}_3\)). This process is named after its inventors, Charles Hall and Paul Héroult, who independently discovered it in 1886. The Hall process is crucial for aluminum production and involves several key steps:

• First, alumina is dissolved in molten cryolite, a mineral that helps lower the melting point of the mixture.
• An electric current is then passed through the molten mixture. This current causes the aluminum ions in the solution to migrate to the cathode (the negative electrode), where they gain electrons and form pure aluminum metal.
• The oxygen ions move towards the anode (the positive electrode) and react with the carbon from the graphite anode, forming carbon dioxide gas.

This electrolytic process is essential in the industrial production of aluminum, as it allows the extraction of aluminum metal from alumina effectively and efficiently. The balanced chemical equation representing the simplified reaction in the Hall process is:\[2\text{Al}_2\text{O}_3(s) + 2\text{C}(s) \rightarrow 4\text{Al}(s) + 3\text{CO}_2(g)\]

aluminum production

Aluminum production is a significant industrial process that involves extracting aluminum metal from its ores, primarily bauxite. Once mined, the bauxite ore is refined into alumina using the Bayer process. This involves crushing the bauxite and treating it with sodium hydroxide to remove impurities and obtain pure alumina.

After the Bayer process, aluminum production moves to the electrolytic stage using the Hall process, where alumina is converted to aluminum metal. Understanding each step in this process helps to appreciate the scale and complexity of aluminum manufacturing:

• Bayer Process: This initial stage targets separating aluminum oxide from the bauxite ore, yielding an alumina-rich solution.
• Hall Process: The aluminum ions in alumina are electrolyzed in molten cryolite to form aluminum metal at the cathode, while oxygen forms carbon dioxide at the anode.

The efficiency and reliability of these processes enable the production of aluminum in large quantities, forming the backbone of industries such as transportation, construction, and packaging.

chemical reactions

Chemical reactions are the fundamental processes by which substances undergo chemical change, transforming into different substances. Balancing chemical equations is crucial to understanding these reactions, especially in industrial processes like the Hall process.

A balanced chemical equation ensures that the same number of each type of atom appears on both sides of the equation. This reflects the law of conservation of mass, meaning mass is neither created nor destroyed in a chemical reaction. Here's a breakdown of how it applies to the Hall process:

• Identify: Start by identifying all reactants and products, as seen in the conversion of alumina and carbon to aluminum and carbon dioxide.
• Count Atoms: Tally the number of each type of atom present in both reactants and products. Adjust the coefficients of the chemical equations to ensure each element has identical counts on both sides.
• Combine Fractions: Avoid fractions where possible for clarity, as demonstrated in the balanced equation for aluminum production.

Understanding these steps helps deepen comprehension of the Hall process and related reactions, thus aiding in accurate prediction and manipulation of chemical production processes.