Answers (1)
Strong acid or base means it ionizes completely in water. It has nothing to do with concentration or corrosiveness. There are seven strong acids:
Sulfuric
Nitric
Hydrochloric
Chloric
Perchloric
Hydrobromic
Hydroiodic
It's easy to remember the list because there are three of the most common industrial acids, three "chloric" acids, three "hydro" acids, and they all make a clumsy "7" on the periodic table.
There are dozens of strong bases and hundreds of "almost strong" bases. A buffer is a mixture of a weak acid and a weak base. The two neutralize each other, but because they are only partially dissolved, they only partially neutralize and the pH of the mixture is determined by their solubility constants. If anything causes the pH to shift up or down, either the base or the acid will dissolve some more, maintaining the pH at a constant value.
Hydrochloric acid is a strong acid, so it is not used in a buffer.