Chemistry - Coordination Chemistry Question with Solution | TestHub

${\left[\mathrm{Co}(\mathrm{CN}{)}_6\right]}^{3-}$ ion is pale yellow in colour because it absorb colour in visible zone.

${\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]}^{3+}$ is blue in colour in due to because it absorb light from ultraviolet zone.

If Silica gel contains ${\left[{\mathrm{CoCl}}_4\right]}^{2-}$ as an indicator when, activated silica gel become dark blue while upon absorbtion of moisture its colour changes to pink

Philospher's Wool is white at room temperature but turns yellow when heated due to metal excess defects.