Final answer:
The more acidic compound can be identified by looking at factors such as atomic size, electronegativity, and conjugate base stability; larger atoms and more electronegative atoms within a molecule often suggest greater acidity.
Step-by-step explanation:
To identify the more acidic compound without using a pKa table, we can look at various factors such as atomic size, electronegativity, and the stability of the conjugate base. For instance, in the case of the pair HSO⁴⁻ or HSeO⁴⁻, we would predict HSeO⁴⁻ to be more acidic because selenium is larger than sulfur, which allows it to better accommodate the negative charge of its conjugate base. As another example, between NH₃ and H₂O, H₂O is more acidic due to oxygen being more electronegative than nitrogen, thus stabilizing the negative charge on its conjugate base more effectively.
In the case of comparing B(OH)₃ and Al(OH)₃, we would look at the periodic table and recognize that aluminum is below boron, meaning it is larger and can better stabilize the negative charge on its conjugate base, making Al(OH)₃ more acidic. Similarly, comparing NH₃ and H₂S, H₂S is the more acidic compound because sulfur is beneath nitrogen in the periodic table, again allowing for better stabilization of the negative charge on its conjugate base.