Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. What is its nature?

Ammonia (NH₃) is a base, meaning it can accept a proton (H⁺). When ammonia dissolves in water, it reacts slightly with water molecules:

NH₃ + H₂O ⇌ NH₄⁺ + OH⁻

In this reaction, ammonia takes a proton from water and becomes ammonium (NH₄⁺). The water molecule that loses the proton forms a hydroxide ion (OH⁻). These OH⁻ ions make the solution alkaline, raising its pH.

Because of this, ammonia turns red litmus paper blue, which is a typical test for bases.

Chemists sometimes write this solution as ammonium hydroxide (NH₄OH), though in reality it is mainly a mixture of NH₃, NH₄⁺, OH⁻, and water in equilibrium.