The formation of the iron III -thiocyanate complex ion equilibrium is affected by changes in pH due to the involvement of ions in the reaction. The reaction can be represented as follows:Fe aq + SCN aq FeSCN aq In this reaction, iron III ions Fe react with thiocyanate ions SCN to form the iron III -thiocyanate complex ion FeSCN . The equilibrium constant for this reaction is given by:K = [FeSCN] / [Fe][SCN] Now, let's consider how changes in pH can affect this equilibrium:1. Increase in pH more basic conditions : When the pH increases, the concentration of H ions in the solution decreases. Thiocyanate ions can react with H ions to form HSCN, which reduces the concentration of SCN ions available for the formation of the complex:H aq + SCN aq HSCN aq Under more basic conditions, this reaction shifts to the left, increasing the concentration of SCN ions. As a result, the formation of the iron III -thiocyanate complex ion is favored, and the equilibrium shifts to the right.2. Decrease in pH more acidic conditions : When the pH decreases, the concentration of H ions in the solution increases. This leads to an increase in the formation of HSCN, which reduces the concentration of SCN ions available for the formation of the complex. Consequently, the equilibrium shifts to the left, disfavoring the formation of the iron III -thiocyanate complex ion.In summary, an increase in pH more basic conditions favors the formation of the iron III -thiocyanate complex ion, while a decrease in pH more acidic conditions disfavors its formation.