Changing the pH of a solution can significantly affect the formation of a complex ion with copper II ion and ethylenediamine. To understand this, let's first look at the chemical equation for the formation of the complex ion:Cu + 2en [Cu en ]Here, Cu represents the copper II ion, and en represents ethylenediamine HNCHCHNH . The complex ion formed is [Cu en ].Now, let's consider the effect of pH on this reaction. The pH of a solution is a measure of the concentration of hydrogen ions H present in the solution. A low pH indicates a high concentration of H ions acidic conditions , while a high pH indicates a low concentration of H ions basic conditions .Ethylenediamine is a bidentate ligand, meaning it can form two coordinate covalent bonds with the copper II ion. The nitrogen atoms in the ethylenediamine molecule have lone pairs of electrons that can form these coordinate covalent bonds. However, under acidic conditions low pH , the nitrogen atoms in ethylenediamine can become protonated, forming NH groups:HNCHCHNH + 2H HNCHCHNHWhen the nitrogen atoms are protonated, they are no longer able to form coordinate covalent bonds with the copper II ion, as their lone pairs of electrons are now involved in bonding with the hydrogen ions. This means that the formation of the complex ion [Cu en ] is inhibited under acidic conditions.On the other hand, under basic conditions high pH , the concentration of H ions is low, and the ethylenediamine molecules are less likely to be protonated. This allows the nitrogen atoms to form coordinate covalent bonds with the copper II ion, promoting the formation of the complex ion [Cu en ].In summary, changing the pH of a solution can affect the formation of a complex ion with copper II ion and ethylenediamine. Acidic conditions low pH inhibit the formation of the complex ion, while basic conditions high pH promote its formation.