MediumChemistryHigh School (11–12)Coordination Compounds › Bonding: Valence Bond and Crystal Field TheoryNumerical
Two complexes of the same metal ion form at 298 K…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Two complexes of the same metal ion form at . The first uses a monodentate ligand and has . The second uses a chelating ligand with the same kind of donor atoms and has . Find for each, in kJ/mol. Which complex is more stable?
Need a reminder? The key ideaShow
A d-d transition absorbs light of wavelength , and for a or ion in kJ/mol with in nm. The colour seen is opposite the colour absorbed. A or ion has no d-d transition. At , in kJ/mol, where is the stability constant.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The first complex. .
Step 2. The second complex. .
Step 3. Compare. The second value is far more negative, and its stability constant is larger by a factor of .
Answer: and . The chelate complex is much more stable.
Why. Each chelating ligand replaces several water molecules, so disorder rises and the free energy falls.
Discussion (0)
Log in to join the discussion.
Loading…