The pH of a solution can significantly affect the formation of a complex ion by influencing the availability of the ligands and the stability of the complex ion formed. In the case of the coordination reaction between a copper II ion and ammonia, the pH plays a crucial role in determining the extent of complex formation.Copper II ions Cu can form a complex ion with ammonia NH as a ligand. The coordination reaction can be represented as follows:Cu aq + 4NH aq [Cu NH ] aq In this reaction, the copper II ion forms a complex ion with four ammonia molecules, resulting in the formation of the tetraamminecopper II complex ion, [Cu NH ].The pH of the solution affects the availability of ammonia molecules to act as ligands. At low pH acidic conditions , the ammonia molecules can react with the excess H ions present in the solution, forming ammonium ions NH :NH aq + H aq NH aq The formation of ammonium ions reduces the concentration of free ammonia molecules available to form the complex ion with copper II ions. As a result, the equilibrium of the coordination reaction shifts to the left, and the formation of the [Cu NH ] complex ion is less favored.On the other hand, at high pH alkaline conditions , the concentration of H ions is low, and the ammonia molecules remain mostly unprotonated. This increases the availability of free ammonia molecules to act as ligands, favoring the formation of the [Cu NH ] complex ion.In summary, the pH of a solution can significantly affect the formation of a complex ion by influencing the availability of ligands and the stability of the complex ion. In the case of the coordination reaction between a copper II ion and ammonia, higher pH alkaline conditions favors the formation of the [Cu NH ] complex ion, while lower pH acidic conditions reduces the extent of complex formation.