Final answer:
A solution with equal concentrations of hydrogen ions and hydroxide ions is neutral. The pH of such a solution is 7, indicating neither acidic nor basic characteristics.
Step-by-step explanation:
A solution containing equal numbers of hydrogen ions (H3O+*) and hydroxide ions (OH-) is neutral. In a neutral solution, the concentration of hydronium ions [H3O+*] and hydroxide ions [OH-] are both equal to 1 × 10-7 M. This condition is in line with the autoprotolysis equilibrium of water.
When measuring acidity or alkalinity, we refer to the pH scale, where the pH value represents the negative logarithm of the hydronium ion concentration (-log[H3O+*]). A pH of 7 is considered neutral, which corresponds to a hydronium ion concentration of 1 × 10-7 M. If the concentration of hydronium ions is higher than this value, the solution is acidic; if lower, the solution is basic or alkaline.