Chapter 21, Problem 108IP

a. In the absorption spectrum of the complex ion Cr(NCS)₆³⁻, there is a band corresponding to the absorption of a photon of light with an energy of 1.75 × 10⁴ cm^-1. Given 1 cm⁻¹ = 1.986 × 10⁻²³ J, what is the wavelength of this photon?

b. The Cr—N—C bond angle in Cr(NCS)₆³⁻ is predicted to be 180°. What is the hybridization of the N atom in the Ncs- ligand when a Lewis acid-base reaction occurs between Cr³⁺ and NCs- that would give a 180° Cr−N−C bond angle? Cr(NCS)₆³⁻ undergoes substitution by ethylenediamine (en) according to the equation

$\text{Cr}{\left(\text{NCS}\right)}_6{}^{3-}+2\text{en}\to \text{Cr}{\left(\text{NCS}\right)}_2{\left(\text{en}\right)}_2{}^{+}+4{\text{NCS}}^{-}$

Does Cr(NCS)₂(en)₂⁺ exhibit geometric isomerism? Does Cr(NCS)₂(en)₂⁺ exhibit optical isomerism?