Ammonia solution contains the hydroxide ions, OH-, which are responsible for its basic properties and high pH. The dissociation of ammonia in water leads to the formation of these hydroxide ions, which can contribute to the alkalinity of the solution.

The reaction that occurs when ammonia dissolves in water is as follows:

NH3 + H2O ⇌ NH4+ + OH-

In this reaction, ammonia molecule reacts with water to form ammonium ions NH4+ and hydroxide ions OH-. The presence of hydroxide ions in the solution increases its pH, making it more basic.

For a solution with a pH of 10 at room temperature, the concentration of hydroxide ions [OH-] can be calculated using the following formula:

[OH-] = 10^(-pH) = 10^(-10) M = 1 x 10^-10 M

Therefore, in an ammonia solution with a pH of 10, the hydroxide ions (OH-) are responsible for the basic nature and high pH of the solution.