How do you tell if an acid is strong or weak?

Answer 1

It is a matter of memorization. There are only 6 common strong acids, some sources list 7 or 8. All other acids can be considered weak.

The six commonly listed strong acids are:

Hydrochloric acid: HCl

Hydrobromic acid: HBr

Hydroiodic acid: HI

Perchloric acid: HClO4

Nitric acid: HNO3

Sulfuric acid: H2SO4

Two acids sometimes cited as strong acids are:

Periodic acid: HIO4

Chloric acid: HClO3

Answer 2

One way to determine whether an acid is strong or weak is to examine its degree of ionization in water. Strong acids completely ionize in water, while weak acids only partially ionize. Additionally, strong acids tend to have higher Ka values compared to weak acids.