Problem 34 - General Chemistry: Principles and Modern Applications

Question

In \(1825,\) Hans Oersted produced aluminum chloride by passing chlorine over a heated mixture of carbon and aluminum oxide. In 1827 , Friedrich Wöhler obtained aluminum by heating aluminum chloride with potassium. Write plausible equations for these reactions.

Step-by-Step Solution

Answer

The balanced equations for the reactions are: 2Al2O3 + 9C + 6Cl2 -> 4AlCl3 + 9CO2 and AlCl3 + 3K -> Al + 3KCl.

Step 1: Write Equation for First Reaction

In the first reaction, get chlorine gas to react with a heated mixture of carbon and aluminum oxide to produce aluminum chloride. The unbalanced equation would look like this: Al2O3 + C + Cl2 -> AlCl3 + CO2. To balance this equation, correct the reactants and products so the number of each type of atom on each side of the equation is the same: 2Al2O3 + 9C + 6Cl2 -> 4AlCl3 + 9CO2.

Step 2: Write Equation for Second Reaction

In the second reaction, Friedrich Wöhler obtained aluminum by heating aluminum chloride with potassium. The unbalanced equation would be: AlCl3 + K -> Al + KCl. To balance this, correct the amounts of reactants and products so they match on both sides of the equation. The resulting balanced equation is: AlCl3 + 3K -> Al + 3KCl.

Step 3: Double Check the Balanced Equations

After writing the balanced reactions, it is always essential to double-check to ensure that the number of each atom in the reactants equals the number in the products. Double-check the work in steps 1 and 2 to verify they are accurately balanced. This truth assures the mass conservation principle in chemistry.

Key Concepts

Aluminum Chloride

Aluminum chloride (AlCl₃) is an important compound in both industrial and laboratory chemistry. It is often used as a catalyst in various chemical reactions and is essential in the production of a range of everyday products.
Aluminum chloride is formed through a chemical reaction involving chlorine gas and aluminum. When these reactants are combined, aluminum chloride is the resultant compound.
This compound is known for its ability to act as a 'Lewis acid', meaning it can accept electron pairs from other molecules. This property makes it incredibly useful in processes like the Friedel-Crafts reaction, which is a key step in the synthesis of many organic compounds. Understanding the basics of aluminum chloride is crucial, as it helps in comprehending how many reactions in industrial chemistry are facilitated.

Aluminum Oxide

Aluminum oxide (Al₂O₃) is a solid compound consisting of aluminum and oxygen. It's widely found in nature as the mineral corundum. Many gemstones, such as sapphires and rubies, owe their coloring to impurities within the aluminum oxide.
This compound is particularly significant in reactions involving aluminum because it forms a durable protective layer on the metal surface. This layer shields it from further reaction with oxygen or other elements that may cause corrosion.
In the scenario described in the exercise, aluminum oxide reacts with chlorine to form aluminum chloride. This reaction highlights aluminum oxide's role as a starting material in producing aluminum-related compounds. Recognizing how it transforms during chemical reactions is key to mastering chemical equations and transformations.

Balancing Chemical Equations

Balancing chemical equations is a fundamental skill in chemistry. Ensuring that equations are balanced guarantees that the mass and number of atoms are conserved, adhering to the law of conservation of mass.
The first step in balancing an equation is to write down the unbalanced equation, listing all reactants and products. Then, adjust the coefficients so that the number of each type of atom is the same on both sides of the equation.
For example, in the exercise's first reaction, the unbalanced equation is \( \text{Al}_2\text{O}_3 + \text{C} + \text{Cl}_2 \rightarrow \text{AlCl}_3 + \text{CO}_2 \). By adjusting the coefficients, the balanced equation becomes \( 2\text{Al}_2\text{O}_3 + 9\text{C} + 6\text{Cl}_2 \rightarrow 4\text{AlCl}_3 + 9\text{CO}_2 \).
Understanding and practicing this skill allows students to predict and visualize chemical transformations efficiently, underpinning a profound understanding of chemical processes and reactions.