Question

Hexacyano complexes of metals in their +2 oxidation state are usually yellow while the corresponding hexaaqua compounds are often blue or green. This is so because?

• A. hexacyano complexes absorb orange or red light thus appear yellow while hexaaqua complexes absorb indigo thus appear yellow.
• B. hexacyano complexes absorb indigo thus appearing yellow while hexaqua complexes absorb orange or red light this appear blue or green
• C. hexacyano complexes absorb yellow light while hexaaqua complexes absorb blue light
• D. $C{N}^{-}$ ions are yellow in colour while aqua ions are blue or green colour.

Answer 1

Answer: (B)

hexacyano complexes absorb indigo thus appearing yellow while hexaqua complexes absorb orange or red light this appear blue or green

Hexa cyano complex absorb indigo due to their strong field ligand thus appear yellow while hexa aqua complex absorb red light due to the weak field ligand thus appear blue or green.