In the context of acid-base chemistry, understanding the predominant forms of a compound at a given pH is crucial. When analyzing a solution at a pH of 8.0, we first identify the most predominant form, which in this case is the intermediate form 2. To determine the second most predominant form, we can utilize the concept of the isoelectric point (pI).

The isoelectric point can be calculated using the formula:

$$ \text{pH} = \frac{1}{2} (\text{pKa}_2 + \text{pKa}_3) $$

For this scenario, we are given pKa values of 5.97 and 9.28. Plugging these values into the formula yields:

$$ \text{pH} = \frac{1}{2} (5.97 + 9.28) = 7.625 $$

This calculated isoelectric pH of 7.625 serves as a baseline for comparison. If the solution's pH is above this value, it indicates a more basic environment, which facilitates the deprotonation of species. Since our current pH of 8.0 is greater than 7.625, we conclude that the second most predominant form in this basic environment is the anionic form, specifically A^3-.

Conversely, if the pH were below 7.625, the environment would be more acidic, leading to protonation and making the intermediate form H₂A^- the second most predominant form. Thus, the isoelectric point provides a critical reference for determining the distribution of species in solution based on pH, allowing us to identify the second most dominant form effectively.