Is #HCl# a strong acid or strong base? How is the determined?

1 Answer
Feb 25, 2017

Answer:

#"Hydrogen chloride"# is a #"strong acid"#.

Explanation:

Acidity (and we usually specify an aqueous solvent) is assessed on the basis of the completeness of the following equilibrium:

#HCl(g) + H_2O(l) rightleftharpoons H_3O^(+) + Cl^-#

Hydrogen chloride is acidic because it increases the concentration of the characteristic cation of the solvent, i.e. #H_3O^+#, #"the hydronium ion"#.

On the other hand, hydrogen fluoride is a weak acid, because the equivalent equilibrium lies farther to the left:

#HF(l) + H_2O(l) rightleftharpoons H_3O^(+) + F^-#

Fluoride is a stronger base than chloride, and hence hydrogen fluoride is a weak acid.