Cobalt Complexes and Equilibrium

Problem In order to intensify the idea of equilibrium and the dependence on temperature, cobalt complexes are useful with a mixture of water molecules and chloride ions as ligands for cobalt complexes the blue colored tetra chloro cobalt complex proves stable in heat, the pink colored hexa aqua cobalt complex in the cold solution, respectively. A cross-linkage to the idea of equilibrium (see Chap. 6) is possible. 

Material Test tubes, burner cobalt(II) chloride solution, concentrated hydrochloric acid, sodium chloride. 

Procedure Add hydrochloric acid to the pink-colored cobalt chloride solution, dilute the obtained blue-colored solution with water. Put cobalt chloride 

Observation The color of the solution changes from pink to blue when hydrochloric acid is added when diluted with water the pink color returns. When the second solution is heated, the blue color appears however, this changes again to pink when solution is cooled off. 

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