A solution of ammonia is alkaline, why?

Ammonia (NH3) is a weak base, meaning that it can accept protons (H+) from water molecules to form ammonium ions (NH4+) and hydroxide ions (OH-). This reaction increases the concentration of hydroxide ions in the solution, making it alkaline. Therefore, a solution of ammonia is alkaline due to the presence of hydroxide ions.

Explanation:

When ammonia (NH3) dissolves in water, it undergoes a chemical reaction with water molecules to form ammonium ions (NH4+) and hydroxide ions (OH-):

NH3 + H2O → NH4+ + OH-

The hydroxide ions (OH-) react with hydrogen ions (H+) in water to form water molecules (H2O), making the solution alkaline:

OH- + H+ → H2O

Increased pH:

The presence of hydroxide ions increases the pH of the solution. The pH scale measures the concentration of H+ ions in a solution, with a lower pH indicating a higher concentration of H+ ions (acidic) and a higher pH indicating a lower concentration of H+ ions (alkaline).

Basic Properties:

Ammonium ions (NH4+) are also weak acids. However, in aqueous solutions, the reaction between NH3 and water produces more hydroxide ions than hydronium ions (H3O+), resulting in an alkaline solution.

Therefore, a solution of ammonia is alkaline because the reaction of ammonia with water produces hydroxide ions, which increase the pH and make the solution basic.