Question

Explain why a precipitate of silver chloride dissolves in NH₄OH.

Answer 1

1. Silver chloride (AgCl) precipitate is insoluble in water and nitric acid.
2. When NH₄OH (ammonium hydroxide) is added, it provides NH₃ molecules.
3. NH₃ acts as a Lewis base due to the lone pair on nitrogen.
4. NH₃ donates its lone pair to the Ag⁺ ion, forming a soluble complex ion, [Ag(NH₃)₂]⁺.
5. This complex ion dissolves in NH₄OH, causing the AgCl precipitate to dissolve.
6. The reaction is \[\ce{AgCl + 2 NH4OH -> [Ag(NH3)2]Cl + 2 H2O}\].

Thus, AgCl dissolves in NH₄OH due to complex ion formation.