NH3 + H2O ------> NH4+ + OH-
Therefore, the hydroxyl ions lend the properties of a base to aqueous ammonia solution, meaning that added to water, the ammonia gas acts as a base. A base is any substance with a pH of more than 7. We can also say that a base is any substance (aqueous) that can accept protons. This solution would therefore react with an acidic solution to form a salt and water. This process is known as 'neutralization'.