Thermodynamics of the [CoCl(iPrOH)3]+ to [CoCl(iPrOH)2(MeOH)3]+ Reaction: A General Chemistry Laboratory Exercise

In this general chemistry laboratory exercise, the absorbance of [CoCl(iPrOH)3]+, where iPrOH is isopropyl alcohol, is used to determine the equilibrium constants for its reaction with methanol to form [CoCl(iPrOH)2(MeOH)3]+ in the temperature range ∼10 to 20 °C. The absorbance versus concentration calibration plot is determined by sequential additions of a concentrated [CoCl(iPrOH)3]Cl standard to iPrOH. The equilibrium mixture is cooled in a CaCl2–ice bath, and measurements of temperature and absorbance are made at various time intervals as the solution warms to room temperature. The variation in the equilibrium constant as a function of temperature is used to determine the Gibbs energy, enthalpy, and entropy.