Question

What is the effect of increasing the pH on the formation of the Cu(NH3)4^2+ complex ion if the initial concentration of Cu2+ and NH3 are 0.1 M and 0.5 M, respectively, assuming a total volume of 500 mL?

Answer 1

Increasing the pH of the solution will result in an increase in the formation of the Cu NH3 4^2+ complex ion. This is because increasing the pH means increasing the concentration of hydroxide ions  OH-  in the solution, which in turn will decrease the concentration of H+ ions. The formation of the Cu NH3 4^2+ complex ion is a result of the reaction between Cu2+ ions and NH3 molecules. The reaction can be represented as follows:Cu2+ + 4NH3 -> Cu NH3 4^2+As the pH increases, the concentration of NH3 will also increase due to the following equilibrium reaction:NH4+ + OH- <-> NH3 + H2OThis means that more NH3 molecules will be available to react with Cu2+ ions, promoting the formation of the Cu NH3 4^2+ complex ion. As a result, increasing the pH will favor the formation of the Cu NH3 4^2+ complex ion in the solution.