University of Central Florida (UCF) CHM2046 Chemistry Fundamentals II Test 3 Practice Test

To determine the strongest acid from a list of acids using their Ka values, you focus on the acid dissociation constant, Ka. The strength of an acid is directly related to its ability to dissociate into ions in solution. The larger the Ka value, the more extensively the acid ionizes in water, indicating a stronger acid.

When you compare the Ka values of different acids, the one with the highest Ka indicates that it dissociates more completely, generating a greater concentration of hydrogen ions (H⁺) in solution. This is evidence of a more effective acid when applying the concept of acid strength. Therefore, selecting the acid with the highest Ka value correlates directly with its strength as an acid.

In context, understanding pKa (the negative logarithm of Ka) can also be useful, as a lower pKa value indicates a higher Ka and therefore a stronger acid. However, choosing based strictly on Ka values, which are absolute and not logarithmic, provides a more straightforward assessment of the acid's strength. So, identifying the strongest acid involves selecting the one with the highest Ka value.