Question

What happens when $S{O_3}$ is passed through water?

Answer 1

We need to understand the reaction between $S{O_3}$ and water. $S{O_3}$ is the chemical formula of a compound called sulphur trioxide. Sulfur trioxide is a colorless liquid in most cases. Sulfur trioxide comes in a variety of forms, including a gaseous monomer, a crystalline trimmer, and a solid polymer. Sulfur trioxide is a solid with a narrow liquid range at just below room temperature. It can also exist as ice- or fiber-like crystals, as well as as a gas.

Complete answer:
When exposed to air, sulfur trioxide quickly absorbs water and emits white odors. Sulfur trioxide is the anhydride of sulphuric acid. Thus, it is susceptible to hydration. Due to sulfuric acid mist production, gaseous sulfur trioxide fumes abundantly even in a relatively dry environment. Hence, when it is passed through water, it reacts vigorously to form sulphuric acid. The reaction is as follows:
$S{O_3} + {H_2}O \to {H_2}S{O_4}$

Additional information:
We have to remember that in sulfonation processes, sulphur trioxide is used as a reagent. Detergents, dyes, and pharmaceuticals are all made possible by these procedures. Sulfur trioxide is either produced in situ or utilised as a solution in sulfuric acid. Sulfur trioxide is a strong sulfonating agent, meaning it can add $S{O_3}$ groups to a wide range of substrates. Organic substrates are often used. Lewis base adducts of sulphur trioxide are efficient sulfonating agents for activated substrates.

Note:
We must note that $S{O_3}$ is also called a sulfuric oxide and sulfuric anhydride. Also, the enthalpy of hydration of the reaction of sulfur trioxide with water is $- 200kJmo{l^{ - 1}}$. It is a strong lewis acid that forms adducts with lewis bases.