Question

What is the colour of ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$.?

Answer 1

1. Potassium dichromate (${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$) is an inorganic chemical reagent and is used as a strong oxidizing agent.
2. The molar mass and melting point of the potassium dichromate is $294.185{\mathrm{gmol}}^{-1}$and $398°\mathrm{C}$.
3. It is a red-orange salt which is soluble in water. The colour significance of this salt is shown below:
4. The chemical colour is due to the d-d orbital transition.
5. Colour is due to Ligand Metal Charge Transfer (LMCT) in which the electron transfer from ${\mathrm{O}}_2$ ligand to the empty d-orbital of the central atom (${\mathrm{Cr}}^{6+}$).