Final answer:
A substance that acts as a proton acceptor and yields hydroxyl ions when dissolved in water is known as a base, such as NaOH. The hydroxide ion (OH⁻) in these bases can accept protons, following the Brønsted-Lowry theory, leading to neutralization reactions in water.
Step-by-step explanation:
A substance that yields hydroxyl ions when dissolved in water and acts as proton acceptors is called a base according to the Brønsted-Lowry theory of acids and bases. Bases typically dissociate in water to form metal cations and hydroxide anions (OH⁻), making the solution basic. A common example of such a substance is sodium hydroxide (NaOH), where the hydroxide ion is the strong Brønsted base that can accept protons from hydronium ions to form water. This is also known as the neutralization process. Water itself can also act as a Brønsted-Lowry base when it accepts a proton. For instance, in the reaction with acetic acid, water acts as a Brønsted-Lowry base accepting a proton from acetic acid to form hydronium ion (H3O⁺). A common example of a base ionization is when C6H5NH₂ (aniline) reacts with water, accepting a proton and forming an OH⁻ ion.