Answer to Question #109927 in General Chemistry for Akash Sharma

Question

An aqueous solution of NiSO4 is green in colour which turns deep blue on addition of ethylenediamine.

Answer 1

In aqueous solution green color is due to aqueous complex [Ni(H2O)6]²⁺, in which the splitting between t_2g and e_g orbitals has energy corresponding to the absorbable of red light (600 nm), so that the visible color is green. Ethylenediamine (en) turns nickel to the complex [Nien3]²⁺ which has a larger splitting energy between t_2g and e_g orbitals corresponding to the absorbance of orange-yellow light, so that the observed transmitted light is deep blue