Fluorosulfonic acid

Fluorosulfonic acid, also called fluorosulfuric acid, is a chemical compound related to sulfuric acid. It is an inorganic sulfonic acid where a fluorine atom replaces one of the  groups attached to the sulfur atom in sulfuric acid. The chemical formula of fluorosulfonic acid is . It is a superacid and the strongest known simple Brønsted acid.

 Properties 
The fluorine atom is more electronegative than the group it replaced. This makes fluorosulfonic acid stronger than sulfuric acid. Acids stronger than sulfuric acid are called superacids. Fluorosulfonic acid can also be mixed with antimony pentafluoride to make an even stronger superacid called magic acid.

Fluorosulfonic acid is the mixed acid anhydride of  and . As an anhydride, it is vulnerable to hydrolysis, and reacts violently with water to make sulfuric acid and hydrofluoric acid:

 Preparation 
Fluorosulfonic acid is made from sulfur trioxide and hydrogen fluoride. Because it reacts with water, anhydrous chemicals must be used. The chemical equilibrium

means that there will always be small amounts of  and  in fluorosulfonic acid, which can damage glass containers by making hexafluorosilicic acid and silicon tetrafluoride.

 References 

Category:Superacids
Category:Oxoacids
Category:Fluorine compounds
Category:Sulfur compounds