What is a strong base?

• A. A base that completely ionises giving OH- ions in solution.
• B. A base that partially ionises in solution.
• C. A base that does not ionise in water.
• D. A base that reacts with acids to form salts.

Answer: (A)

A strong base is one that completely ionizes in water to produce hydroxide ions. When a base dissociates fully, every molecule releases OH-, so the solution has a high concentration of hydroxide ions and a high pH. This rapid, complete dissociation differentiates strong bases from weak bases, which only partially ionize and produce fewer OH- ions at equilibrium. A base that does not ionize in water would not contribute OH- to the solution and wouldn’t act as a base in that context. While bases can react with acids to form salts, the defining idea here is the extent of ionization in solution.