In the context of acid-base theory, what role does a conjugate base play?

A conjugate base is formed when an acid donates a proton (H⁺ ion) to a base. In this context, the conjugate base has the ability to accept protons, which reflects its role in acid-base reactions. This is based on the Brønsted-Lowry definition of acids and bases, where an acid is a proton donor and a base is a proton acceptor.

When an acid loses a proton, the species that remains is called the conjugate base. For example, when hydrochloric acid (HCl) donates a proton, it becomes the conjugate base chloride ion (Cl⁻). This chloride ion can now promote the reverse reaction by accepting a proton under certain conditions, demonstrating the function of a conjugate base in the equilibrium of acid-base reactions.

The other choices do not accurately describe the role of a conjugate base. A conjugate base does not donate protons, does not inherently stabilize solutions, and is not simply a neutral ion; it can exist as a charged species that has the potential to engage in further acid-base reactions.