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How does sulfur trioxide react with water?

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Sulfur trioxide ( $S O_{3}$ ) is the acid anhydride of sulfuric acid, and it reacts violently with water to form sulfuric acid.123

This chemical reaction is highly exothermic, meaning it releases a significant amount of heat. Because of its reactivity, sulfur trioxide fumes vigorously when exposed to moist air. When dissolved in concentrated sulfuric acid, it forms a solution known as fuming sulfuric acid, or oleum.132