A strong acid typically has what value of pKa?

A strong acid is characterized by its ability to completely dissociate in solution, yielding a high concentration of hydrogen ions (H⁺). The pKa value is a logarithmic measure of the acid's strength; specifically, it is the negative logarithm (to base 10) of the acid dissociation constant (Ka).

For strong acids, such as hydrochloric acid (HCl) or sulfuric acid (H₂SO₄), the dissociation constant (Ka) is very large, which makes the pKa notably low. A strong acid typically has a pKa value that is significantly less than zero, often around -1 to -3, indicating that the acid is very effective at donating protons in solution.

Values greater than 20 signify very weak acids, and values around 7 correspond to neutral substances rather than strong acids. Consequently, the range of pKa for strong acids is correctly identified as being less than -2, which indicates a high degree of dissociation and consequently strong acidity.