When ammonia is added to a cupric salt solution, the deep blue colour is observed it is due to the f — d and f Block Elements Chemistry Question

💡 Solution & Explanation

Step 1: Cupric (Cu2+) ions in water form a light blue hydrated complex. Adding excess ammonia triggers a ligand-substitution reaction. Step 2: The water molecules are displaced by ammonia ligands to form a stable coordination complex: [Cu(H2O)4]^2+ + 4NH3 -> [Cu(NH3)4]^2+ + 4H2O. Step 3: The resulting tetraamminecopper(II) complex, [Cu(NH3)4]^2+, exhibits a highly intense, deep blue color in solution, matching option (b).