Final answer:
Salicylic acid predominantly exists as its conjugate base in blood plasma due to the pH of the plasma being significantly higher than the pKa of salicylic acid.
Step-by-step explanation:
Given that the pKa of salicylic acid is 2.97, we can determine how it will behave in a solution such as blood plasma, which has a pH range of 7.35-7.45. The pKa is a measure of the strength of an acid, indicating the pH at which half of the acid molecules are deprotonated. Since the pH of blood plasma is significantly higher than the pKa of salicylic acid, we would expect that salicylic acid would exist predominantly in its conjugate base form in the plasma.
Applying the Henderson-Hasselbalch equation, we can estimate the ratio of the acid to its conjugate base. For a weak acid HA and its conjugate base A−, the equation is pH = pKa + log([A−]/[HA]). If pH is greater than pKa, the log ratio will be positive, and thus [A−] > [HA], meaning the conjugate base is favored.
Therefore, we can conclude that salicylic acid in blood plasma will primarily be in the form of its conjugate base, salicylate (C6H4OHCO2−), which will lead to deprotonation and a higher concentration of the conjugate base in solution compared to the un-ionized salicylic acid.