Facial (fac) and meridional (mer) isomers are types of geometric isomers found in octahedral complexes with the general formula \([MA_3B_3]\). In these complexes, three identical ligands can either be adjacent to each other forming a 'facial' configuration or adjacent to form a 'meridional' configuration.
Let's analyze why the other complexes do not show fac-mer isomerism:
Thus, the correct complex exhibiting facial-meridional isomerism is \([Co(NH_3)_3Cl_3]\).
To determine which complex shows facial-meridional isomerism, we first need to understand what these terms mean:
Now, let's evaluate the given complexes:
\([Co(NH_3)_3Cl_3]\): This complex can display facial-meridional isomerism as it is an octahedral complex with three amine ligands and three chloride ligands, allowing for both fac-arrangement (three Cl or NH3 occupy one face) and mer-arrangement (three Cl or NH3 in a plane).
\([Co(NH_3)_4Cl_2]^+\): This complex cannot exhibit this isomerism as it lacks three identical ligands that could form a face.
\([Co(en)_3]^{3+}\): This complex is homoleptic, consisting of three ethylenediamine (\(en\)) ligands that do not allow for facial-meridional distinction.
\([Co(en)_2Cl_2]^+\): Similar to the above, this complex cannot show facial-meridional isomerism as it has only two Cl ions, preventing the formation necessary for fac-mer isomerism.
Thus, the correct complex that shows facial-meridional isomerism is:
\([Co(NH_3)_3Cl_3]\)
What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)

Cobalt chloride when dissolved in water forms pink colored complex $X$ which has octahedral geometry. This solution on treating with cone $HCl$ forms deep blue complex, $\underline{Y}$ which has a $\underline{Z}$ geometry $X, Y$ and $Z$, respectively, are
| List I (Substances) | List II (Element Present) |
| (A) Ziegler catalyst | (I) Rhodium |
| (B) Blood Pigment | (II) Cobalt |
| (C) Wilkinson catalyst | (III) Iron |
| (D) Vitamin B12 | (IV) Titanium |
| List-I (Complex ion) | List-II (Spin only magnetic moment in B.M.) |
|---|---|
| (A) [Cr(NH$_3$)$_6$]$^{3+}$ | (I) 4.90 |
| (B) [NiCl$_4$]$^{2-}$ | (II) 3.87 |
| (C) [CoF$_6$]$^{3-}$ | (III) 0.0 |
| (D) [Ni(CN)$_4$]$^{2-}$ | (IV) 2.83 |
What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)