An aqueous solution of metal ion M1 reacts separately with reagents Q and R in excess to give tetrahedral and square planar complexes, respectively. An aqueous solution of another metal ion M2 always forms tetrahedral complexes with these reagents. The aqueous solution of M2 on reaction with reagent S gives the white precipitate which dissolves in excess of S. The reactions are summarized in the given below. Tetrahedral Q←−−−−excessM1R−−−−→excess Square planar
Tetrahedral Q←−−−−excessM2R−−−−→excess Tetrahedral
↓S, Stoichiometric amount
White precipitate S−−−−→excess precipitate dissolves