The crystal field stabilization energy (CFSE) of \left [ Fe\left ( H_{2}O \right )_{6} \right ]Cl_{2}  and K_{2}\left [ NiCl_{4} \right ] , respectively , are :

  • Option 1)

    -0.6\Delta _{0} \; and\; -0.8\Delta _{t}

  • Option 2)

     -0.4\Delta _{0}\; and\; -0.8\Delta _{t}       

  • Option 3)

    -2.4\Delta _{0}\; and\; -1.2\Delta _{t}

  • Option 4)

     -0.4\Delta _{0}\; and\; -1.2\Delta _{t}

Answers (1)

(a) CFSE of \left [ Fe\left ( H_{2}O \right )_{6} \right ]Cl_{2}\rightarrow \left [ Fe \left ( H_{2}O \right )_{6} \right ]^{2+}+2Cl^{-}

Fe^{2+}\rightarrow \left [ Ar \right ]3d^{6}

H_{2}O is weak ligands so pairing not take place 

t_{2g}^{2.1.1}     eg.1.1

CFSE=-0.4\times 4\Delta _{0}+0.6\times 2\Delta _{0}=-0.4\Delta _{0} 

(b) CFSE of K_{2}\left [ NiCl_{4} \right ]

                   Ni^{2+}\rightarrow \left [ Ar \right ]3d

             Cl^{-}\rightarrow weak field ligand pairing not take place & also have tetrahedra geometry.

              e.g.^{2.2}    ,  t_{2g}^{2.1.1}

       CFSE=-0.6\times 4\Delta _{t}+0.4\times 4\Delta _{t}=0.8\Delta _{t}


Option 1)

-0.6\Delta _{0} \; and\; -0.8\Delta _{t}

Option 2)

 -0.4\Delta _{0}\; and\; -0.8\Delta _{t}       

Option 3)

-2.4\Delta _{0}\; and\; -1.2\Delta _{t}

Option 4)

 -0.4\Delta _{0}\; and\; -1.2\Delta _{t}

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