Answer the following questions:
(A) [Ni(H 2 O) 6 ] 2+ (aq) is green in colour whereas [Ni(H 2 O) 4 (en)] 2+ (aq)is blue in colour , give reason in support of your answer .
(A) The colour of coordination compounds depends upon the type of ligand and dd transition taking place .
H 2 O is a weak field ligand , which causes small splitting , leading to the d-d transition corresponding to green colour .
However due to the presence of ( en ) which is a strong field ligand , the splitting is increased .
Due to the change in t2g -eg splitting the colouration of the compound changes from green to blue .