Question

What would happen to the color of the solution in part (b) if a small amount of \({\bf{NaOH}}\) were added and \({\bf{Fe}}\left( {{\bf{OH}}} \right){\bf{3}}\) precipitated? Explain your answer.

Short answer

The solution will become lighter.

Step-by-step solution

Step 1: What would happen to the color of the solution.

The reaction

• The solution is dark because of the concentration of\({\rm{Fe}}{({\rm{SCN}})^{2 + }}\)
  A small amount of \({\rm{NaOH}}\)were added and\(\begin{array}{l}{\rm{Fe}}{({\rm{OH}})_3}\\\end{array}\)precipitated

The formation of\(\begin{array}{l}{\rm{Fe}}{({\rm{OH}})_3}\\\end{array}\), decreases the concentration of\({\rm{F}}{{\rm{e}}^{3 + }}\).
The decrease in the\({\rm{F}}{{\rm{e}}^{3 + }}\)concentration shifts the equilibrium to the left, decreasing the concentration of\({\rm{Fe}}{({\rm{SCN}})^{2 + }}\), and the solution becomes lighter.