Answer to Question #230985 in Chemistry for ZaZa

Question

When ammonia gas (NH3) is bubbled through water that contains a few drops of phenolphthalein indicator, the water turn pink.Explain how the Bronsted Lowry theory of acids and bases can account for this observation,supporting your response with a chemical equation 

Answer 1

The Brønsted-Lowry theory defines an acid as a proton donor and a base as a proton acceptor. In this theory, the reaction of an acid and base is represented as an equilibrium reaction. acid (1) + base (2) ⇌ base (1) + acid (2)

Acid (1) and base (1) are called a conjugate acid-base pair, as are acid (2) and base (2).

The phenolphthalein turns pink because the ammonia dissolved in the water causes the water to become base: NH_3(g) + H₂O_(l) = NH₄⁺_(aq) + OH^-_(aq)