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Answer the following.
Answer the following: On the basis of Valence Bond Theory (VBT), state the following regarding…
Answer the following:
(a)[1.6666666666666667]
On the basis of Valence Bond Theory (VBT), state the following regarding $[\text{CoF}_6]^{3-}$ complex ion:
(Atomic Number of $\text{Co} = 27$)
(1) Oxidation state of cobalt
(2) Type of hybridisation of the central metal atom
(3) Magnetic behaviour of the complex
(4) IUPAC name of the complex
(b)[1.6666666666666667]
Consider the complex ions $[\text{Fe}(\text{CN})_6]^{3-}$ and $[\text{Fe}(\text{CN})_6]^{4-}$.
Which complex ion will be attracted towards applied magnetic field? Justify your answer with a reason.
(Atomic Number of $\text{Fe} = 26$)
(c)[1.6666666666666667]
What types of isomerism do the following pairs of compounds show?
(1) $[\text{Co}(\text{NH}_3)_5\text{Br}]\text{SO}_4$ and $[\text{Co}(\text{NH}_3)_5\text{SO}_4]\text{Br}$
(2) $[\text{Cr}(\text{H}_2\text{O})_4\text{Cl}_2]\text{Cl}\cdot 2\text{H}_2\text{O}$ and $[\text{Cr}(\text{H}_2\text{O})_5\text{Cl}]\text{Cl}_2\cdot\text{H}_2\text{O}$
Answer
Answer (a)
AI| IUPAC name | hexafluoridocobaltate(III) ion |
| Oxidation state | 3 |
| Hybridisation | sp3d2 |
| Magnetic behaviour | paramagnetic |
(1) Oxidation state of Co: $x - 6 = -3$, so $+3$. (2) $\mathrm{Co^{3+}}$ is $3d^6$; $\mathrm{F^-}$ is a weak-field ligand, so no pairing occurs and the $4s$, $4p$ and two $4d$ orbitals are used: $sp^3d^2$ (outer orbital, octahedral). (3) 4 unpaired electrons: paramagnetic. (4) Hexafluoridocobaltate(III) ion.
Answer (b)
AI$[\mathrm{Fe(CN)_6}]^{3-}$ is attracted by the magnetic field. Because $\mathrm{Fe^{3+}}$ is $3d^5$ and $\mathrm{CN^-}$ is a strong-field ligand, the electrons pair up to give $t_{2g}^5$ with one unpaired electron (paramagnetic), whereas in $[\mathrm{Fe(CN)_6}]^{4-}$, $\mathrm{Fe^{2+}}$ is $3d^6$ giving $t_{2g}^6$ with no unpaired electrons (diamagnetic).
Answer (c)
AI(1) Ionisation isomerism
(2) Hydrate isomerism
From ISC 2026 Improvement Chemistry Paper 1, question 21(i).
Check your working with the Coordination complex analyser: hybridisation, shape, magnetic moment, CFSE, isomers and the IUPAC name of a complex.