Which of the following is the correctly balanced equation for the reaction of aluminum with hydroxide ions in a basic solution to form aluminate ions and hydrogen gas?

• A. Al + OH⁻ → AlO₂⁻ + H₂
• B. 2 Al + 4 OH⁻ → 2 AlO₂⁻ + 2 H₂
• C. 2 Al + 2 OH⁻ → 2 AlO₂⁻ + H₂
• D. Al + 2 OH⁻ → AlO₂⁻ + H₂

Answer: (B)

Verified step by step guidance

1. Identify the reactants and products in the given chemical reaction: Aluminum (Al), hydroxide ions (OH⁻), aluminate ions (AlO₂⁻), and hydrogen gas (H₂).
2. Write the unbalanced chemical equation: Al + OH⁻ → AlO₂⁻ + H₂.
3. Balance the number of aluminum atoms on both sides of the equation. Since there is one aluminum atom on both sides, it is already balanced.
4. Balance the number of oxygen and hydrogen atoms. Notice that each AlO₂⁻ ion contains two oxygen atoms, so you need two OH⁻ ions to provide these. This also gives you two hydrogen atoms, which can form one H₂ molecule.
5. Check the overall charge balance. The left side has a charge of -2 from 2 OH⁻ ions, and the right side has a charge of -2 from 1 AlO₂⁻ ion. Therefore, the balanced equation is: Al + 2 OH⁻ → AlO₂⁻ + H₂.