How does sulfur dioxide contribute to the formation of acid rain?

Sulfur dioxide plays a significant role in the formation of acid rain due to its ability to dissolve in rainwater, leading to the formation of sulfurous acid. When sulfur dioxide is released into the atmosphere, particularly from sources such as volcanic eruptions or industrial processes, it can easily combine with water vapor present in the atmosphere.

As it interacts with the moisture, a chemical reaction occurs, resulting in the production of sulfurous acid. This process is crucial because sulfurous acid can further react with oxygen in the presence of water to form sulfuric acid, which is a stronger acid. When precipitation occurs, the sulfuric and sulfurous acids dissolve in the rainwater, leading to acidic rainfall. This acid rain can harm ecosystems, corrodes buildings and monuments, and affects soil chemistry.

The other choices do not accurately describe the impact of sulfur dioxide in the context of acid rain formation. While evaporation and reactions with heavy metals are processes that can occur, they do not directly lead to the generation of acid rain. Similarly, the combustion process releasing carbon monoxide does not involve sulfur dioxide's role in acid formation. Thus, the connection between sulfur dioxide, its reaction with water, and acid formation underscores its contribution to acid rain.