Problem 52 - Chemistry The Science in Context

Question

Aluminum reacts with elemental oxygen at high temperatures to give pure aluminum oxide. What is the coefficient of \(\mathrm{O}_{2}(\mathrm{g})\) in the balanced chemical equation?

Step-by-Step Solution

Answer

Answer: The coefficient of O2(g) in the balanced chemical equation is 3.

Step 1: Write the unbalanced chemical equation

First, identify the reactants and products in the given reaction. Aluminum (Al) reacts with elemental oxygen (O2) to form aluminum oxide (Al2O3). Write the unbalanced equation: Al + O2 -> Al2O3

Step 2: Balance the oxygen atoms

To balance the oxygen atoms, we recognize that there are 2 oxygen atoms on the left side of the equation (in O2) and 3 oxygen atoms on the right side (in Al2O3). The least common multiple of 2 and 3 is 6, so we need to have 6 oxygen atoms on both sides of the equation. To achieve this, multiply both O2 and Al2O3 by a suitable coefficient. 3 (Al + O2 -> Al2O3) This gives us: Al + 3O2 -> 2Al2O3 Now there are six oxygen atoms on both sides of the equation.

Step 3: Balance the aluminum atoms

Currently, there is 1 aluminum atom on the left side of the equation and 4 aluminum atoms on the right side (2Al2O3). To balance the aluminum atoms, we need to multiply the aluminum (Al) on the left side by a suitable coefficient. 4Al + 3O2 -> 2Al2O3 Now there are four aluminum atoms on both sides of the equation. The equation is now balanced.

Step 4: Identify the coefficient of O2(g)

Now that the chemical equation is balanced, we can identify the coefficient for O2(g). In the final balanced equation: 4Al + 3O2 -> 2Al2O3 The coefficient of O2(g) is 3.

Key Concepts

Balancing Equations

Balancing chemical equations is a fundamental skill in chemistry that ensures the law of conservation of mass is obeyed in a reaction. This means that the number of each type of atom must be the same on both sides of the equation. When balancing an equation, remember these key steps:

• Identify the reactants and the products.
• Write down the unbalanced equation with all reactants and products.
• Balance each type of atom one at a time. It often helps to start with the element that appears in the fewest compounds.
• Adjust coefficients as necessary to balance the atoms. Remember that coefficients are placed before the compounds or elements in the equation.

In the exercise, the unbalanced reaction of aluminum with oxygen gas is first written as \( \text{Al} + \text{O}_{2} \rightarrow \text{Al}_{2}\text{O}_{3} \). By following the steps, we adjust the coefficients to ensure an equal number of each element on both sides, resulting in the balanced equation \( 4\text{Al} + 3\text{O}_{2} \rightarrow 2\text{Al}_{2}\text{O}_{3} \).

Stoichiometry

Stoichiometry involves the calculation of reactants and products in a chemical reaction, using the balanced equation as a guide. This aspect of chemistry is crucial for predicting the quantities of substances consumed and produced in reactions.Once an equation is balanced, stoichiometry allows you to compute the precise amounts of each substance involved.

• Coefficients in the balanced equation indicate the mole ratio of reactants to products.
• This ratio helps in determining how much of one reactant is needed to completely react with another, or how much product can be formed from certain reactants.
• Use the mole ratio to convert between the number of moles of different substances in a reaction.

In the balanced equation \( 4\text{Al} + 3\text{O}_{2} \rightarrow 2\text{Al}_{2}\text{O}_{3} \), the stoichiometric coefficients (4:3:2) indicate that four moles of aluminum react with three moles of oxygen to form two moles of aluminum oxide.

Aluminum Oxide

Aluminum oxide is a chemical compound comprised of aluminum and oxygen, commonly found in the mineral known as bauxite. It is characterized by its chemical formula \(\text{Al}_{2}\text{O}_{3}\).Aluminum oxide is very important in industrial settings due to its hardness and strength. Here are a few key properties and applications:

• It is used as an abrasive due to its high melting point and resistance to wear.
• Aluminum oxide serves as a refractory material, which means it can withstand very high temperatures without breaking down.
• The compound is also used in the production of aluminum metal through electrolytic processes.

The reaction to form aluminum oxide involves aluminum reacting with oxygen gas at high temperatures, signifying its creation in environments with strong oxidizing conditions. Understanding these characteristics is essential not only from a chemical standpoint but also for practical applications across various industries.