Final answer:
The Brønsted-Lowry theory defines an acid as a proton donor and a base as a proton acceptor. In an acid-base reaction, a proton is transferred from the acid to the base, forming a conjugate acid-base pair. Examples include HCl (acid) and its conjugate base Cl-, as well as NH3 (base) and its conjugate acid NH4+.
Step-by-step explanation:
According to the Brønsted-Lowry theory, an acid is a substance that can donate a proton (hydrogen ion, H+), while a base is a substance that can accept a proton. During an acid-base reaction, a proton transfer occurs from the acid to the base.
A conjugate acid-base pair consists of two species that differ by the presence or absence of a proton. The species that arises from a base by gaining a proton is the conjugate acid, while the species that results from an acid losing a proton is the conjugate base. For example, in the dissociation of hydrochloric acid (HCl), HCl acts as the Brønsted-Lowry acid, and its conjugate base is the chloride ion (Cl-).
To further clarify, consider the reaction between ammonia (NH3) and water (H2O). NH3 acts as the Brønsted-Lowry base and accepts a proton from water, thus water is the Brønsted-Lowry acid. The products of this reaction are the ammonium ion (NH4+), which is the conjugate acid of ammonia, and hydroxide ion (OH-), which is the conjugate base of water.