When the concentration of hydronium ions [H3O+] is greater than hydroxide ions [OH-], the solution is considered?

In a solution, if the concentration of hydronium ions (([H_3O^+])) exceeds that of hydroxide ions (([OH^-])), the solution is classified as acidic. This is rooted in the definitions of acid-base chemistry, where an acid is characterized by its ability to donate protons, resulting in an increase in hydronium ion concentration.

In acidic solutions, the pH is below 7, reflecting a higher concentration of (H_3O^+) than (OH^-). Conversely, in neutral solutions, these two concentrations are equal, and in basic solutions, (OH^-) predominates. Understanding this relationship between the concentrations of hydronium and hydroxide ions is essential for identifying the nature of solutions and their reactions. Therefore, when determining the acidity of a solution, the dominance of (H_3O^+) confirms its classification as acidic.