Calcium ions reacting with ammonia yield what?

• A. White precipitate.
• B. No precipitate or faint white precipitate.
• C. Green precipitate.
• D. Blue precipitate.

Answer: (B)

Calcium ions can form calcium hydroxide when hydroxide ions are present, but Ca(OH)2 is only sparingly soluble. Whether a solid appears depends on how much OH− is available. Ammonia is a weak base, so it provides only a small amount of OH−; that isn’t enough to push the calcium hydroxide equilibrium toward precipitation, so you don’t see a visible solid (or you might see only a very faint white speck). If a strong base like sodium hydroxide were used, the higher OH− concentration would drive precipitation readily, giving a clear white solid.