Which term describes an acid (or base) that ionizes completely in water?

• A. pH
• B. Strong acid (or base)
• C. pOH
• D. Buffer Solution

Answer: (B)

In aqueous solutions, acids and bases that ionize completely are described as strong acids and strong bases. This means they dissociate 100% into their ions—strong acids fully produce hydronium ions (H3O+) and their conjugate bases, while strong bases fully yield hydroxide ions (OH−). The extent of ionization is effectively complete, which is reflected by very large Ka (for acids) or Kb (for bases) values, making the equilibrium lie far to the right. This contrasts with weak acids and bases, which only partially ionize and establish a balance between ionized and unionized forms.

Examples include hydrochloric acid and other strong mineral acids, which donate protons readily, and sodium hydroxide or potassium hydroxide, which dissociate completely to give OH−. The other terms like pH or pOH describe the acidity or basicity of the solution, not the degree of ionization, and a buffer solution is designed to resist pH change and typically involves species that do not ionize completely.