BITSAT2018ChemistryCoordination CompoundsActual
Which of the following is the correct order for the wavelength if absorption in the visible region.
Options
- ANi NO 2 6 4 - < Ni NH 3 6 2 + < Ni H 2 O 6 2 +
- BNi NO 2 6 4 - < Ni H 2 O 6 2 + < Ni NH 3 6 2 +
- CNi H 2 O 6 2 + < Ni NH 3 6 2 + < Ni NO 2 6 4 -
- DNi NH 3 6 2 + < Ni H 2 O 6 2 + < Ni NO 2 6 4 -
Correct answer
A. Ni NO 2 6 4 - < Ni NH 3 6 2 + < Ni H 2 O 6 2 +
Step-by-step solution
When central metal ion is same (here Ni 2 + ), the absorption of colour depends on the ligand. According to spectrochemical series, various ligands are as follows I < Br - < Cl - < NO 3 - < F - < H 2 O < NH 3 < NO 2 - < CN - < CO Thus, H 2 O is the weakest ligand among these, therefore the absorbed energy will be lowest in Ni H 2 O 6 2 + , so it will absorb highest wavelength (red light). E ∝ 1 λ ∴ The order of increasing wavelength is Ni NO 2 6 4 - < Ni NH 3