What Happens When Ammonia Is Mixed With Water?

As ammonia dissolves in water, it reacts with water to form ammonium ions (NH4+) and hydroxide ions (OH-):

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'.

You its the rite answer but none has given the name for the formulae
its ammonium hydroxide ( NH_4^OH) which is a basic solution

Ammonia is represented by the formula NH₃. It acts as a base when it is dissolved in water and it increases the pH of water and changes the neutral pH of water to a little basic pH. Ammonia is readily dissolved in water and almost 67% of the ammonia molecules are protonated. This means that when you will dissolve ammonia in water, you will get basic solution of NH₄OH.

Ammonia may be acidic as it dissociates nh4+  and particularity when nh4+ are in major quantity ammonia is acidic if you are not convinced then you can see what happens when nh4 reacts with pure distilled water??  Hope you find my opinion correct.