What are the different types of acids?

Question

What are the different types of acids?

Answer 1

There are numerous was to categorize different acids.  Here are a few different ways you can divide up different types.

There are two general types of acids:  strong acids and weak acids.  There are only a few strong acids, and so ALL the others are considered weak.  See the Related Questions for a complete list of the strong acids (and strong bases too).

Strong acids are considered strong because they dissociate completely in water to form the same number of moles of hydrogen ions (H+) as the number of moles of acid added to water.  Therefore, for a strong acid, you can determine the pH of the solution simply by knowing the concentration of the acid (again, see the Related Questions for how to do this).

Weak acids on the other hand, do not dissociate completely in water.  Some examples of weak acids are acetic acid (found in vinegar), carbonic acid, hydrofluoric acid, and formic acid.  Note that just because an acid is called "weak" does NOT mean that it is not dangerous!  Hydrofluoric acid (HF) is a weak acid and is one of the most dangerous acids of all of them!  In order to determine the pH of a solution of a weak acid, you must know two things:  the concentration of the acid in the solution, and also something called the Ka of the acid (or equivalently the pKa, which is just equal to -log10Ka).  The Ka is a measure of how much the acid will dissociate.  A higher Ka value (and a lower pKa!) means that the acid will dissociate more.

There are also other ways to categorize acids.  The most common types of acids are those that release H+ when added to water.  These include hydrochloric acid (HCl), sulfuric acid (H2SO4), acetic acid for example.  However, there are other acids that do not release H+ ions!  Some examples of this type of acid are aluminum chloride (AlCl3), iron(III) chloride (FeCl3), and boron trifluoride (BF3).  What makes these acid is instead that the central metal (Al, Fe, or B in the examples here) are electron deficient.  An acid can also be defined as something which accepts an electron pair (a Lewis acid).  This is in fact the most general definition of an acid, and include ones that donate a proton also.

Finally, there are other ways to categorize acids, such as "mineral acids," "organic acids," "superacids