MCQ
Which of the following is spin-free complex?
- ✓$[Fe(H_2O)_6] Cl_2$
- B$K_4[Fe(CN)_6$
- C$[Ni(CO)_4]$
- D$[Ni(CN)_4]^{2-}$

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Atomic mass of $\mathrm{K}=39, \mathrm{Mn}=55, \mathrm{O}=16]$
$\mathrm{HX}(\mathrm{aq}) \rightleftharpoons \mathrm{H}^{+}(\mathrm{aq})+\mathrm{X}(\mathrm{aq}), \mathrm{Ka}=1.2 \times 10^{-5}$
$\left[\mathrm{K}_{\mathrm{n}}:\right.$ dissociation constant]
The osmotic pressure of $0.03 \mathrm{M}$ aqueous solution of $\mathrm{HX}$ at $300 \mathrm{~K}$ is ............... $\times 10^{-2}$ bar (nearest integer).
$\left[\right.$ Given : $\mathrm{R}=0.083 \mathrm{~L} \mathrm{bar} \mathrm{Mol}^{-1} \mathrm{~K}^{-1}$ ]