Which statement about alkalis is true?

• A. They are acids.
• B. They do not interact with water.
• C. They dissolve in water to form hydronium ions.
• D. They are a type of base that dissolves in water and produces hydroxide ions.

Answer: (D)

Alkalis are soluble bases that dissolve in water and release hydroxide ions, which makes the solution alkaline. That’s why the statement describing them as a type of base that dissolves in water and produces hydroxide ions is true. For example, when a compound like sodium hydroxide dissolves, it dissociates into sodium ions and hydroxide ions (OH−); the presence of OH− is what raises the pH. The other options mix up acid behavior (acids form hydronium ions in water) or ignore the key point that alkalis must dissolve in water to affect the solution, and note that some bases aren’t soluble and thus aren’t alkalis.