Q. Which of the following complex is paramagnetic with two unpaired electrons ?

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$K_{3}\left[Fe \left(\right. CN \left(\left.\right)_{6}\right]$

$K_{2}\left[NiCl_{4}\right]$

$K_{2}\left[CoCl_{4}\right]$

$\left(Na\right)_{2}\left[Ni \left(\right. CN \left(\left.\right)_{4}\right]$

Solution:

$K_{2}\left[NiCl_{4}\right]Ni^{+ 2}$
$\left(Cl\right)^{-}\left(\right.WFL\left.\right)$ . So No pairing of $e^{-}$ takes place. Hence it is paramagnetic with two unpaired $e^{-}$

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$ E _{ O _{2} / H _{2} O }^{\circ}=+1.223 \,V$
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