Resumen de Gibbs Energy Changes during Cobalt Complexation: A Thermodynamics Experiment for the General Chemistry Laboratory
Michael J. DeGrand, M. Leigh Abrams, Judith L. Jenkins, Lawrence E. Welch
By adding a large quantity of Cl− to an aqueous solution of CoCl2·6H2O, a mixture containing a red octahedral cobalt complex and a blue tetrahedral complex is produced. When the solution temperature is modified, the equilibrium constant, Keq, of the complexation reaction is shifted and the proportion of the two colored forms altered correspondingly. Absorbance spectrophotometry is utilized to determine the concentration of each cobalt species, allowing Keq and the change in Gibbs energy, ΔG°, values to be found at each temperature tested. By plotting ΔG° versus temperature, the changes in entropy and enthalpy for the reaction can be determined.
