Discussion Forum



1)

 Which of the following compounds is not coloured yellow ?


A) $Zn_{2}[Fe(CN)_{6}]$

B) $Zn_{2}[Fe(CN)_{6}]$

C) $(NH_{4})_{3}[As(Mo_{3}O_{10})_{4}]$

D) $BaCrO_{4}$

Answer:

Option A

Explanation:

$Zn_{2}[Fe(CN)_{6}], K_{3}[Co(NO_{2})_{6}) and  [(NH_{4})_{3}As (Mo_{3}O_{10})_{4}]$  show colour due to d-d  transition while BaCrO4  is coloured  due to charge transfer phenomenon.

  Further , accroding to spectrochemical  series the strong ligand possessing complex has higher  energy  and hence lower wavelength. Therefore , complexes containing   $NO_{2}.NH_{4}^{+}.O^{2-}$   etc. ligands show yellow  colour while CN -  forces the complex to impart white colour

 Spectrochemical series

  I- < Br- < S2-  < SCN- <Cl-  

                      <NO3 - < N3-  <F-  <OH-

  < C2 O42-  =H2O< NCS-  < CH3 CN

                       <py  <NH3  <en <bipy

< Phan <NO2 <PPh3  <CN-  = CO