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Answer the following.
Answer the following: When the coordination compound is mixed with solution, three moles of are…
Answer the following:
(a)[1.0]
When the coordination compound $\text{CoCl}_3\cdot6\text{NH}_3$ is mixed with $\text{AgNO}_3$ solution, three moles of $\text{AgCl}$ are precipitated per mole of the compound. Write the structural formula of the complex compound.
(b)[1.0]
Predict the number of unpaired electrons in $[\text{Fe}(\text{H}_2\text{O})_6]^{3+}$ and $[\text{Fe}(\text{CN})_6]^{3-}$ based on crystal field theory.
(c)[1.0]
Draw a diagram to show the splitting of d-orbitals in a tetrahedral crystal field.
Draw: Splitting of d-orbitals in a tetrahedral crystal field
(d)[2.0]
Write the formulae for the following:
(1) Linkage isomer of $[\text{CoCl}(\text{en})_2(\text{NO}_2)]\text{Cl}_2$
(2) Ionisation isomer of $[\text{CoBr}(\text{NH}_3)_5]\text{SO}_4$
Answer
Answer (a)
Official answer key| Formula | [Co(NH3)6]Cl3 |
Three moles of AgCl per mole means all three $\mathrm{Cl^-}$ are ionisable (outside the coordination sphere): $[\mathrm{Co(NH_3)_6}]\mathrm{Cl_3} \rightarrow [\mathrm{Co(NH_3)_6}]^{3+} + 3\mathrm{Cl^-}$.
Answer (b)
Official answer key$[\mathrm{Fe(H_2O)_6}]^{3+}$: weak field ligand, $t_{2g}^3 e_g^2$, 5 unpaired electrons.
$[\mathrm{Fe(CN)_6}]^{3-}$: strong field ligand, $t_{2g}^5 e_g^0$, 1 unpaired electron.
Answer (c)
Official answer keyIn a tetrahedral field the five d orbitals split into a lower set of two ($e$: $d_{x^2-y^2}$, $d_{z^2}$) and a higher set of three ($t_2$: $d_{xy}$, $d_{yz}$, $d_{zx}$), with splitting $\Delta_t$; the $t_2$ set is $\frac{2}{5}\Delta_t$ above and the $e$ set $\frac{3}{5}\Delta_t$ below the average energy (barycentre).
Answer (d)
Official answer key(1) Linkage isomer: $[\mathrm{CoCl(en)_2(ONO)}]\mathrm{Cl_2}$ (nitrito-O instead of nitro-N)
(2) Ionisation isomer: $[\mathrm{Co(NH_3)_5SO_4}]\mathrm{Br}$
From ISC 2026 Specimen 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.