How do sulfur trioxide and water react

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Sulfur trioxide occurs in three modifications. As a monomer, sulfur trioxide is only present in the gas phase in equilibrium between planar molecules and their cyclic trimers.

By condensing the vapor, solid γ- is obtained, which consists of corrugated six-membered molecules.

Below room temperature there is a solid, asbestos-like α- and β-: white, silky-shiny needles. The modifications consist of rings and chains of different sizes in which the hybridized sulfur atoms are tetrahedrally surrounded by four oxygen atoms. Strictly speaking, they are modifications of the polysulfuric acids.

The exact structure of α- is not known.

Hazard warnings
  • Sulfur trioxide is hygroscopic; it reacts with water to form sulfuric acid, generating a lot of heat and hissing violently.
  • Due to its volatility, it smokes in moist air and sulfuric acid droplets are formed immediately.
  • is a strong oxidizing agent. For example, it oxidizes sulfur to or from.

The representation of is based on the oxidation of sulfur dioxide to trioxide. This reaction is an equilibrium reaction.