Which of the following describes a base according to the Brønsted-Lowry definition?

According to the Brønsted-Lowry definition, a base is specifically defined as a substance that accepts protons (H⁺ ions). This theory expands the concept of acids and bases beyond the classical definitions that focus solely on hydroxide ion (OH⁻) production in water.

In this context, when a base accepts a proton, it often leads to the formation of its conjugate acid, illustrating the dynamic nature of acid-base reactions. This interaction is critical in many chemical processes and helps account for the behavior of bases in various environments, including aqueous solutions and organic systems.

Understanding this definition allows one to clearly differentiate between acids and bases in chemical reactions. For instance, in a reaction between ammonia (NH₃) and hydrochloric acid (HCl), ammonia acts as the base because it accepts a proton from HCl, resulting in the formation of ammonium (NH₄⁺). This highlights the fundamental role that proton transfer plays in defining a base within the Brønsted-Lowry framework.