Problem 58 - Chemistry: Principles and Reactions

Question

Write balanced equations for the reaction of aluminum metal with the following nonmetals: (a) sulfur (b) bromine (c) nitrogen (d) oxygen (forming \(\mathrm{O}^{2-}\) ions) (e) oxygen (forming \(\mathrm{O}_{2}{\underline{\phantom{xx}}}^{2-}\), or peroxide ions)

Step-by-Step Solution

Answer

(a) \(2\mathrm{Al} + 3\mathrm{S} \rightarrow \mathrm{Al}_{2}\mathrm{S}_{3}\) (b) \(2\mathrm{Al} + 6\mathrm{Br} \rightarrow 2\mathrm{AlBr}_{3}\) (c) \(2\mathrm{Al} + \mathrm{N}_{2} \rightarrow 2\mathrm{AlN}\) (d) \(4\mathrm{Al} + 3\mathrm{O}_{2} \rightarrow 2\mathrm{Al}_{2}\mathrm{O}_{3}\) (e) \(2\mathrm{Al} + 3\mathrm{O}_{2} \rightarrow \mathrm{Al}_{2}(\mathrm{O}_{2})_{3}\)

Step 1: (a) Reaction of aluminum with sulfur

First, we need to determine the compound formed by combining aluminum and sulfur. Aluminum has a charge of +3, and sulfur has a charge of -2. To balance the charges, the formula for the compound is Al2S3. Now, we must balance the equation: \(2\mathrm{Al} + 3\mathrm{S} \rightarrow \mathrm{Al}_{2}\mathrm{S}_{3}\)

Step 2: (b) Reaction of aluminum with bromine

Aluminum has a charge of +3, and bromine has a charge of -1. So, the compound formed by combining them is AlBr3. Now, we must balance the equation: \(2\mathrm{Al} + 6\mathrm{Br} \rightarrow 2\mathrm{AlBr}_{3}\)

Step 3: (c) Reaction of aluminum with nitrogen

Aluminum and nitrogen combine to form aluminum nitride. Aluminum has a charge of +3, and nitrogen has a charge of -3. So, the formula of the compound is AlN. Now, we must balance the equation: \(2\mathrm{Al} + \mathrm{N}_{2} \rightarrow 2\mathrm{AlN}\)

Step 4: (d) Reaction of aluminum with oxygen (forming \(\mathrm{O}^{2-}\) ions)

Aluminum and oxygen combine to form aluminum oxide. Aluminum has a charge of +3, and oxygen (as \(\mathrm{O}^{2-}\) ions) has a charge of -2. The formula for the compound is Al2O3. Now, we must balance the equation: \(4\mathrm{Al} + 3\mathrm{O}_{2} \rightarrow 2\mathrm{Al}_{2}\mathrm{O}_{3}\)

Step 5: (e) Reaction of aluminum with oxygen (forming \(\mathrm{O}_{2}{ }^{2-}\), or peroxide ions)

Aluminum and oxygen can also combine to form aluminum peroxide. In this case, oxygen has a charge of -1, as it forms peroxide ions (\(\mathrm{O}_{2}{\underline{\phantom{xx}}}^{2-}\)). The formula for aluminum peroxide is Al(O2)3. Now, we must balance the equation: \(2\mathrm{Al} + 3\mathrm{O}_{2} \rightarrow \mathrm{Al}_{2}(\mathrm{O}_{2})_{3}\)

Key Concepts

Balancing Chemical Equations

Balancing chemical equations is a crucial skill in chemistry because it ensures that the same amount of atoms for each element are on both sides of the reaction. This reflects the law of conservation of mass, which states that mass cannot be created or destroyed in a chemical reaction. When balancing equations, follow these simple steps:

• Write down the unbalanced equation.
• Count the number of atoms of each element in the reactants and products.
• Add coefficients to balance the atoms on each side.
• Check your work to ensure all atoms balance and the simplest ratio is used.

Remember, we can only change coefficients (the numbers in front of compounds or elements), not the subscripts of the chemical formulas, which denote the number of atoms in a molecule. Balancing equations helps us predict the amount of reactants needed and the products that will form.

Aluminum Compounds

Aluminum is a versatile element that forms various compounds due to its +3 charge. It often reacts with nonmetals to form ionic compounds. In a reaction, each aluminum ion donates three electrons to achieve stability. This property is integral in determining the formula of aluminum's compounds. For example:

• With sulfur, Aluminum forms aluminum sulfide ( Al_2S_3 ).
• With bromine, Aluminum forms aluminum bromide ( AlBr_3 ).
• With nitrogen, Aluminum forms aluminum nitride (AlN).
• With oxygen forming oxide ions, Aluminum forms aluminum oxide ( Al_2O_3 ).
• With oxygen forming peroxide ions, Aluminum can form aluminum peroxide ( Al(O_2)_3 ).

These compounds demonstrate aluminum's ability to adapt to different bonding scenarios, making it an essential metal in various chemical processes.

Reaction with Nonmetals

When metals react with nonmetals, they typically form ionic compounds. These are created through the transfer of electrons, where metals lose electrons to become positively charged ions, and nonmetals gain electrons to become negatively charged ions. For aluminum, a common metal, these reactions are straightforward:

• Reacts with sulfur to form aluminum sulfide ( Al_2S_3 ).
• Reacts with bromine to form aluminum bromide ( AlBr_3 ).
• Reacts with nitrogen to form aluminum nitride (AlN).
• Reacts with oxygen to form either aluminum oxide ( Al_2O_3 ) or aluminum peroxide ( Al(O_2)_3 ).

These reactions demonstrate how mixing aluminum with different nonmetals produces different compounds based on their respective charges and bonding tendencies. Understanding these interactions allows scientists and engineers to predict and manipulate chemical reactions for various applications.

Charges and Formula Determination

Understanding how to determine the charges and formulas of compounds formed between a metal and nonmetals is crucial because it defines the properties and behavior of these compounds. Charge balance is key when forming neutral compounds, which is the goal in most chemical reactions.
For example:

• Aluminum's charge is +3, while oxygen in oxide form is -2. To balance these charges, two aluminum atoms are needed to balance with three oxide ions, forming aluminum oxide ( Al_2O_3 ).
• For aluminum and sulfur, aluminum's +3 charge and sulfur's -2 charge lead to the compound aluminum sulfide ( Al_2S_3 ).
• With nitrogen, both elements have a charge of +3 (Al) and -3 (N), leading to a simple 1:1 ratio in aluminum nitride (AlN).

Consider peroxide ions ( O_2^{2-} ) where oxygen's charge is -1. Aluminum joins with these to form aluminum peroxide ( Al(O_2)_3 ), showcasing the unique bonding possibilities based on charge balance. Balancing charges is the key to determining the correct chemical formula for compounds, allowing scientists to understand how different elements interact.