Question

Write the balanced chemical equation between aluminum hydroxide and sulfuric acid.

Short answer

2 Al(OH)₃ + 3 H₂SO₄ → Al₂(SO₄)₃ + 6 H₂O.

Step-by-step solution

Write the Unbalanced Chemical Equation

Identify the reactants and products of the reaction. Aluminum hydroxide is Al(OH)₃ and sulfuric acid is H₂SO₄. When they react, they form aluminum sulfate Al₂(SO₄)₃ and water H₂O. The unbalanced equation is: \[\text{Al(OH)}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + \text{H}_2\text{O}\]

Balance Aluminum Atoms

Ensure that the number of aluminum atoms on both sides of the equation is the same. Since there are two aluminum atoms in Al₂(SO₄)₃, we need 2 Al(OH)₃: \[2\text{Al(OH)}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + \text{H}_2\text{O}\]

Balance Sulfate Ions

Balance the sulfate ions. There are three sulfate ions in Al₂(SO₄)₃, so we need 3 H₂SO₄: \[2\text{Al(OH)}_3 + 3\text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + \text{H}_2\text{O}\]

Balance Hydrogen and Oxygen Atoms

Finally, balance the number of hydrogen and oxygen atoms. There are 6 hydroxide groups contributing 6 oxygen atoms and 6 hydrogen atoms on the left. Additionally, 3 H₂SO₄ contribute 6 more hydrogen atoms, for a total of 12 hydrogen atoms and 6 oxygen contributed by hydroxide and another 12 by sulfuric acid: \[2\text{Al(OH)}_3 + 3\text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + 6\text{H}_2\text{O}\]

Confirm the Balance

Verify that all atoms are balanced on both sides of the equation. There are 2 aluminum atoms, 3 sulfate ions, 12 hydrogen atoms, and 18 oxygen atoms on both sides, confirming the balance.

Key concepts

Chemical Reactions

A chemical reaction involves the transformation of reactants into products. In the unbalanced equation given in the exercise, aluminum hydroxide \( \text{Al(OH)}_3 \) reacts with sulfuric acid \( \text{H}_2\text{SO}_4 \). After the reaction, the products are aluminum sulfate \( \text{Al}_2(\text{SO}_4)_3 \) and water \( \text{H}_2\text{O} \). Each type of molecule interacts through its atoms leading to product formation.
The central idea is that the reaction rearranges the atoms. They do not change into new atoms; they just form new compounds. It's the breaking and forming of bonds that make up chemical reactions. Ensuring the equation reflects the same number of each kind of atom on both sides of the reaction showcases the law of conservation of mass. No atoms are lost or gained; they are merely shifted.
Understanding these fundamental principles of chemical reactions helps us comprehend how a balanced equation represents the real behavior of chemicals interacting.

Stoichiometry

Stoichiometry is the study of the quantitative relationships, or ratios, between the substances participating in a chemical reaction. In balancing the equation, we use stoichiometry to ensure that for every substance involved, the number of moles is proportional to each element inside each reactant and product.
When balancing our equation between aluminum hydroxide and sulfuric acid, we adjust the coefficients of the compounds to ensure each element's count matches on both sides. For example, 2 mole of \( \text{Al(OH)}_3 \) provides 2 aluminum atoms and we fix sulfuric acid to 3 moles (\( 3\text{H}_2\text{SO}_4 \)) to get the correct number of sulfate ions for the resulting aluminum sulfate.
The coefficients we place in front of each compound ensure all atoms are accounted for. This illustrates stoichiometry as not just about the math but understanding how amounts of substances relate proportionally.

Acid-Base Reactions

The reaction described in the exercise is an acid-base reaction, where an acid reacts with a base to form water and a salt. In this scenario, sulfuric acid \( \text{H}_2\text{SO}_4 \) acts as the acid and aluminum hydroxide \( \text{Al(OH)}_3 \) functions as the base.
In acid-base reactions, the acid donates protons (\( \text{H}^+ \) ions) to the base. This proton exchange results in the formation of water, evidenced in our balanced equation where \( 6\text{H}_2\text{O} \) emerges as a product.
Understanding these reactions helps in predicting product formation when acids and bases meet. The ability to balance this equation hinges on recognizing the acid and base components, anticipating the typical outcome of water, and adjusting moles to align with acid-base reaction principles.