In what type of solution do the concentrations of [H3O+] and [OH-] equal each other?

In solutions where the concentrations of hydronium ions ([H_3O^+]) and hydroxide ions ([OH^-]) are equal, the solution is classified as neutral. This is because, under neutral conditions, the self-ionization of water occurs, resulting in equal concentrations of these ions.

At 25 degrees Celsius, the concentration of ([H_3O^+]) in pure water is (1.0 \times 10^{-7} , \text{M}), which means ([OH^-]) is also (1.0 \times 10^{-7} , \text{M}). This equality of hydronium and hydroxide ion concentrations signifies that the solution neither has excess acidity (acidic solution) nor basicity (basic solution), thus indicating a neutral pH of 7.

Basic solutions have a higher concentration of hydroxide ions than hydronium ions, while acidic solutions have a higher concentration of hydronium ions compared to hydroxide ions. Concentration refers to the amount of solute in a given volume of solution, and can vary independently from the pH balance of hydronium and hydroxide ions, which is not the defining