Which of the following oxides is predicted to form the most basic aqueous solution?

• A. CO2
• B. Na2O
• C. P2O5
• D. SO2

Answer: (B)

Verified step by step guidance

1. Understand that the basicity of an oxide in aqueous solution depends on whether the oxide forms hydroxide ions (OH⁻) when dissolved in water. Metal oxides typically form basic solutions, while nonmetal oxides tend to form acidic solutions.
2. Identify the nature of each oxide: CO₂, P₂O₅, and SO₂ are nonmetal oxides, which generally form acidic solutions by producing acids when dissolved in water (e.g., CO₂ forms carbonic acid). Na₂O is a metal oxide, which usually reacts with water to form hydroxides, resulting in a basic solution.
3. Write the reaction of Na₂O with water to see the formation of hydroxide ions: \(\mathrm{Na_2O + H_2O \rightarrow 2Na^+ + 2OH^-}\), which clearly shows the production of hydroxide ions, making the solution basic.
4. Compare this with the reactions of the nonmetal oxides with water, which produce acids rather than bases (e.g., \(\mathrm{CO_2 + H_2O \rightarrow H_2CO_3}\)), indicating acidic solutions.
5. Conclude that among the given options, Na₂O is predicted to form the most basic aqueous solution because it produces hydroxide ions upon dissolution, unlike the other oxides which form acidic solutions.