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12 Απρ 2023 · As an example of the formation of complex ions, consider the addition of ammonia to an aqueous solution of the hydrated Cu 2+ ion { [Cu (H 2 O) 6] 2+}. Because it is a stronger base than H 2 O, ammonia replaces the water molecules in the hydrated ion to form the [Cu (NH 3) 4 (H 2 O) 2] 2+ ion.
In some cases, ammonia replaces water around the central metal ion to give another soluble complex. This is known as a ligand exchange reaction, and involves an equilibrium such as this one: The formation of this new soluble complex causes the precipitate to dissolve.
The addition of aqueous ammonia to the solution results in the formation of the intensely blue-violet [Cu(NH 3) 4 (H 2 O) 2] 2+ ions, usually written as [Cu(NH 3) 4] 2+ ion (right) because ammonia, a stronger base than H 2 O, replaces water molecules from the hydrated Cu 2+ ion.
As an example of dissolution by complex ion formation, let us consider what happens when we add aqueous ammonia to a mixture of silver chloride and water. Silver chloride dissolves slightly in water, giving a small concentration of Ag + ( [Ag +] = 1.3 × 10 –5 M): AgCl(s) ⇌ Ag+(aq) + Cl − (aq)
Some common ligands include water, ammonia, and other simple molecules that can easily donate a pair of electrons to form a bond with the central atom or ion. Ligands can also be more complex molecules or ions, such as organic compounds or metal ions.
Chemical Equation: NH₃ (g) + H₂O (l) ⇌ NH₄⁺ (aq) + OH⁻ (aq). In this reaction, ammonia reacts with water, a process in which it accepts a proton from a water molecule, resulting in the formation of ammonium ions and hydroxide ions.
We are going to look in detail at the bonding in the complex ion formed when water molecules attach themselves to an aluminium ion to give Al (H 2 O) 63+. Start by thinking about the structure of a naked aluminium ion before the water molecules bond to it.
