Problem 38 - Chemistry and Chemical Reactivity

Question

Write a balanced equation for the reaction of aluminum hydroxide with sulfuric acid.

Step-by-Step Solution

Answer

The balanced equation is \( 2\text{Al(OH)}_3 + 3\text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + 6\text{H}_2\text{O} \).

Step 1: Write the Formula for Reactants

Identify and write the chemical formulas for the reactants. Aluminum hydroxide is written as \( \text{Al(OH)}_3 \) and sulfuric acid is \( \text{H}_2\text{SO}_4 \).

Step 2: Predict the Products

Based on the reaction of a hydroxide and an acid, predict that the products will be a salt and water. The salt formed will be aluminum sulfate \( \text{Al}_2(\text{SO}_4)_3 \) and water is \( \text{H}_2\text{O} \).

Step 3: Write the Unbalanced Equation

Combine the reactants and predicted products into an unbalanced chemical equation: \( \text{Al(OH)}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + \text{H}_2\text{O} \).

Step 4: Balance the Aluminum Atoms

Ensure there is the same number of aluminum atoms on both sides of the equation. Add a coefficient of 2 in front of \( \text{Al(OH)}_3 \): \( 2\text{Al(OH)}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + \text{H}_2\text{O} \).

Step 5: Balance the Sulfate Ions

Balance the sulfate ions by ensuring there are 3 moles of \( \text{H}_2\text{SO}_4 \). Add a coefficient of 3 in front of \( \text{H}_2\text{SO}_4 \): \( 2\text{Al(OH)}_3 + 3\text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + \text{H}_2\text{O} \).

Step 6: Balance the Hydrogen and Oxygen Atoms

Since there are 6 \( \text{OH}^- \) groups and 6 \( \text{H}^+ \) ions from sulfuric acid, there will be 6 molecules of water produced. Add a coefficient of 6 in front of \( \text{H}_2\text{O} \): \( 2\text{Al(OH)}_3 + 3\text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + 6\text{H}_2\text{O} \).

Step 7: Verify the Balanced Equation

Check that all elements have the same number of atoms on both sides of the equation: \( \text{Al} = 2, \text{S} = 3, \text{O} = 15\), and \( \text{H} = 12\). The balanced equation is correct.

Key Concepts

Aluminum Hydroxide

Aluminum hydroxide is a compound with the chemical formula \( \text{Al(OH)}_3 \). It is a white substance that occurs naturally as a mineral, but it can also be produced industrially. This compound is often used in applications such as antacids, water purification, and as a fire retardant due to its chemical properties.

• It acts as a base, reacting with acids to form water and salts.
• One common reaction is with sulfuric acid, which is a key component in balancing the chemical equation we are examining.

Understanding aluminum hydroxide is crucial because its role as a reactant influences the formation of the final products in chemical reactions.

Sulfuric Acid

Sulfuric acid, represented by the chemical formula \( \text{H}_2\text{SO}_4 \), is a highly corrosive strong acid. It is widely used in various industrial processes like fertilizer production and petroleum refining. This acid has two hydrogen atoms that can ionize, making it a dibasic acid with significant reactivity.

• When sulfuric acid reacts with a base like aluminum hydroxide, it results in the production of water and a salt—in this case, aluminum sulfate.
• This reaction is a classic example of an acid-base reaction, leading to neutralization, which is essential for balancing chemical equations.

Understanding sulfuric acid's properties helps predict reaction products and balance them accurately.

Reaction Products

The reaction between aluminum hydroxide and sulfuric acid is an example of an acid-base reaction. Such reactions commonly result in the formation of a salt and water. For this specific reaction:

• The salt produced is aluminum sulfate, \( \text{Al}_2(\text{SO}_4)_3 \).
• The other product is water, \( \text{H}_2\text{O} \).

These products are formed as a result of the complete neutralization of the hydroxide base by the acid. An understanding of these products is key to predicting and balancing the chemical equation. Correctly identifying these outputs ensures our equation is both meaningful and complete.

Chemical Formulas

Chemical formulas play a critical role in expressing the composition of substances involved in chemical reactions.

• They convey what elements are present and in what ratio.
• For instance, aluminum hydroxide is \( \text{Al(OH)}_3 \), indicating one aluminum ion combined with three hydroxide ions.
• Another example is sulfuric acid's formula, \( \text{H}_2\text{SO}_4 \), which suggests it consists of two hydrogen atoms, one sulfur atom, and four oxygen atoms.

Understanding these formulas allows us to correctly predict reaction products and construct balanced chemical equations, ensuring that the law of conservation of mass is upheld.