Why is a solution of [Ni(H 2 O) 6 ] 2+ green, but a solution of [Ni(CN) 4 ] 2– is colourless?

Question

Why is a solution of [Ni(H 2 O) 6 ] 2+ green, but a solution of [Ni(CN) 4 ] 2– is colourless?, The green colour in [Ni(H 2 O) 6 ] 2+ arises from the presence of water ligands, which releasing light in the green region of the electromagnetic spectrum., The cyanide ions in [Ni(CN) 4 ] 2– cause a green colour due to their strong absorption of green light., The green colour of [Ni(H 2 O) 6 ] 2+ is due to the nickel ion's natural colour., [Ni(H 2 O) 6 ] 2+ is green because water is a weak field ligand and it allows unpaired electrons and thus results in d-d transition ultimately resulting in colour but in the case of [Ni(CN) 4 ] 2– , CN - ions pair up the electrons,not allowing transition to happen

MARKS App · Accepted Answer

Correct Option is : (D) [Ni(H 2 O) 6 ] 2+ is green because water is a weak field ligand and it allows unpaired electrons and thus results in d-d transition ultimately resulting in colour but in the case of [Ni(CN) 4 ] 2– , CN - ions pair up the electrons,not allowing transition to happen

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