Q.Ammonia is a good complexing agent. Explain.

Step 1. Identify the source of complexing ability. Section 9.8.3 explains that the lone pair of electrons on ammonia's nitrogen atom facilitates complexation with transition-metal ions — this lone pair is donated into an empty (typically d) orbital on the metal, forming a coordinate covalent (dative) bond.

Step 2. Give the copper example. Cu2+(aq) + 4NH3(aq) → [Cu(NH3)4]2+(aq), a deep-blue complex ion, where four NH3 molecules each donate their lone pair to the central Cu2+.

Step 3. Give the silver example. AgCl(s) + 2NH3(aq) → [Ag(NH3)2]Cl(aq), a colourless, water-soluble complex — this reaction is in fact how a stubborn AgCl precipitate can be redissolved by adding excess ammonia (as also used in Exercise 18). …

Explaining ammonia's Lewis-base (lone-pair-donor) character and illustrating it with the tw …

• Describing ammonia's basicity (reacting with acids to form NH4+) as the same thing as its complexing ability; complexation is specifically about the lone pair coordinating to a METAL ion …