What is an alkali?

• A. A type of base that dissolves in water and produces hydroxide ions (OH-).
• B. A substance that donates electrons.
• C. A measure of acidity.
• D. A type of acid.

Answer: (A)

An alkali is a base that dissolves in water and forms hydroxide ions (OH-) in solution. That production of OH- makes the solution alkaline, with a pH above 7, and it can neutralize acids. Common examples are substances like sodium hydroxide or potassium hydroxide. The reason this best fits is that alkalis are defined by being soluble bases that generate hydroxide ions in water, not by donating electrons, being a general measure of acidity, or being acids themselves.