Sulfur+Trioxide

Sulfur Trioxide is the chemical compound with the formula SO3. In the gaseous form, this is a significant pollutant, being the primary agent in acid rain. It is prepared on massive scales as a precursor to Sulfuric Acid.

Sulfur Trioxide will cause serious burns on both inhalation and ingestion. It should be handled with extreme care as it reacts with water violently and produces highly corrosive sulfuric acid.

SO3 is the anhydride of H2SO4. Thus, the following reaction occurs:

SO3 (l) + H2O (l) → H2SO4 (l) (−88 kJ mol−1)

The reaction occurs both rapidly and exothermically, too violently to be used in large-scale manufacturing. At or above 340 °C, sulfuric acid, sulfur trioxide, and water coexist in significant equilibrium concentrations.

Sulfur trioxide also reacts with sulfur dichloride to yield the useful reagent, thionyl chloride.

SO3 + SCl2 → SOCl2 + SO2

SO3 is a strong Lewis acid readily forming crystalline complexes with pyridine, dioxane and trimethylamine which can be used as sulfonating agents.

Structure and Bonding

 * SO3 is a trigonal planer molecule of D3h symmetry
 * Sulfer Trioxide exhibits hybridization
 * Non-Polar molecule

Application
In process plant environment, SO3 gas is mixed into flue gas from combustion to make the ashes charged up before flowing through electrostatic precipitators. The electrostatic precipitators will then trap the ashes, making cleaner process emission possible.

Safety
Sulfur trioxide will cause serious burns on both inhalation and ingestion since it is highly corrosive and hygroscopic in nature. SO3 should be handled with extreme care as it reacts with water violently and produces highly corrosive sulfuric acid.