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.
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