Changing the pH affects the formation of the Cu NH3 4 2+ complex ion because the reaction involves the coordination of ammonia NH3 molecules to the copper II ion Cu2+ . The reaction can be represented as follows:Cu2+ + 4NH3 <=> Cu NH3 4 2+When the pH is increased i.e., the solution becomes more basic , the concentration of NH3 increases, which shifts the equilibrium to the right, favoring the formation of the Cu NH3 4 2+ complex ion. Conversely, when the pH is decreased i.e., the solution becomes more acidic , the concentration of NH3 decreases, which shifts the equilibrium to the left, disfavoring the formation of the Cu NH3 4 2+ complex ion.To calculate the equilibrium constant Kc for this reaction at different pH values, you need to consider the relationship between pH, pOH, and the concentration of NH3. The pOH can be calculated from the pH using the following equation:pOH = 14 - pHNext, you can calculate the concentration of hydroxide ions OH- using the following equation:[OH-] = 10^-pOH Since ammonia is a weak base, you can use the Kb base dissociation constant of ammonia to find the concentration of NH3. The Kb of ammonia is 1.8 x 10^-5 . The base dissociation reaction for ammonia is:NH3 + H2O <=> NH4+ + OH-The Kb expression for this reaction is:Kb = [NH4+][OH-] /[NH3]Assuming that the initial concentration of NH4+ is negligible, you can set up an ICE Initial, Change, Equilibrium table and solve for the equilibrium concentration of NH3. Once you have the concentration of NH3, you can plug it into the Kc expression for the complex ion formation reaction:Kc = [Cu NH3 4 2+]/ [Cu2+][NH3]^4 You will need the initial concentration of Cu2+ and the equilibrium concentration of Cu NH3 4 2+ to solve for Kc. Note that the Kc value will change with different pH values due to the change in NH3 concentration.