Applying Psuedo-First-Order Methodology to Study Ni-PADA Ligand Substitution with Ammonia

This physical/inorganic chemistry laboratory experiment introduces metal-ligand substitution reactions and spectroscopic determination of forward and reverse rate constants. First, students study various forward and reverse rate constants of reversible first order reactions by applying mathematical models in EXCEL. Then, students apply pseudo first order methodology, reacting excess ammonia with aqueous Ni(II)-pyridine-2-azo-p-dimethylaniline in the formation of hexaaminenickel(II) ion. Using a MicroLAB FS-522 16 wavelength spectrometer, students acquire and analyze data to solve for Ni(II)-PADA and PADA concentrations. Finally, students apply EXCEL SOLVER in determination of forward and reverse rate constants. This guided-inquiry lab was performed in an integrated senior level physical-inorganic chemistry lab.