What is the chemical equation for sulfur dioxide dissolving in water?

The correct answer illustrates the reaction of sulfur dioxide with water, resulting in the formation of sulfurous acid, H₂SO₃. This process can be understood as follows:

When sulfur dioxide (SO₂) dissolves in water (H₂O), it reacts to form H₂SO₃, also known as sulfurous acid. This reaction occurs because sulfur dioxide is a soluble gas that interacts chemically with water, leading to the incorporation of the SO₂ molecule into the structure of sulfurous acid. This compound is important in various chemical processes and environmental phenomena, such as acid rain, where SO₂ plays a significant role.

The other choices include reactions that are not representative of the interaction between sulfur dioxide and water. For example, the formation of sulfuric acid (H₂SO₄) directly from SO₂ and water or involving oxygen does not accurately describe the immediate reaction occurring in aqueous conditions. Additionally, the presence of hydrogen (H₂) does not contribute to the formation of sulfurous acid in this context, as sulfur dioxide does not react with molecular hydrogen in the aqueous environment to produce H₂SO₃. Thus, the straightforward reaction between SO₂ and H₂O yielding sulfurous acid is accurately represented in the correct choice.