Q. Correct increasing order for the wavelengths of absorption in the visible region for the complexes of $Co^{3+}$ is :
A) $[Co(en)_3]^{3+}$, $[Co(NH_3)_6]^{3+}$, $[Co(H_2O)_6]^{3+}$
B) $[Co(H_2O)_6]^{3+}$, $[Co(en)_3]^{3+}$, $[Co(NH_3)_6]^{3+}$
C) $[Co(H_2O)_6]^{3+}$, $[Co(NH_3)_6]^{3+}$, $[Co(en)_3]^{3+}$
D) $[Co(NH_3)_6]^{3+}$, $[Co(en)_3]^{3+}$, $[Co(H_2O)_6]^{3+}$
Explanation
[Solution] Field strength en > $NH_3$ > $H_2O$; larger $\Delta_o$ means shorter wavelength absorbed, so the increasing order of wavelength is en < $NH_3$ < $H_2O$. Answer (1).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.