CBSE 2025 · Region 1 · Set 1 · Q32 · 5 marks
(A)Answer the following :(a)Low spin tetrahedral complexes are not known.(b)$\displaystyle \mathrm{Co}^{2+}$ is easily oxidised to $\displaystyle \mathrm{Co}^{3+}$ in the presence of a strong ligand [At. No. of Co = $\displaystyle 27$](c)What type of isomerism is shown by the complex $\displaystyle \left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]$ $\displaystyle \left[\mathrm{Cr}(\mathrm{CN})_{6}\right]$ ?(d)Why a solution of $\displaystyle \left[\mathrm{Ni}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}$ is green while a solution of $\displaystyle \left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}$ is colourless. (At. No. of $\displaystyle \mathrm{Ni}=28$ )(e)Write the IUPAC name of the following complex : $\displaystyle \left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5}\left(\mathrm{CO}_{3}\right)\right] \mathrm{C} l$ 32. (B) (a) What is meant by 'Chelate effect' ? Give an example. ( $\displaystyle \mathbf{2} \boldsymbol{+} \mathbf{2} \boldsymbol{+} \mathbf{1} \boldsymbol{=} \mathbf{5}$ )(b)Write the hybridization and magnetic behaviour of $\displaystyle \left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-}$. (Atomic number : $\displaystyle \mathrm{Fe}=26$ )(c)If $\displaystyle \mathrm{PtCl}_{2} \cdot 2 \mathrm{NH}_{3}$ does not react with $\displaystyle \mathrm{AgNO}_{3}$, what will be its formula ?
(A)
Answer the following :
(a)
Low spin tetrahedral complexes are not known.
(b)
$\displaystyle \mathrm{Co}^{2+}$ is easily oxidised to $\displaystyle \mathrm{Co}^{3+}$ in the presence of a strong ligand [At. No. of Co = $\displaystyle 27$]
(c)
What type of isomerism is shown by the complex $\displaystyle \left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]$ $\displaystyle \left[\mathrm{Cr}(\mathrm{CN})_{6}\right]$ ?
(d)
Why a solution of $\displaystyle \left[\mathrm{Ni}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}$ is green while a solution of $\displaystyle \left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}$ is colourless. (At. No. of $\displaystyle \mathrm{Ni}=28$ )
(e)
Write the IUPAC name of the following complex : $\displaystyle \left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5}\left(\mathrm{CO}_{3}\right)\right] \mathrm{C} l$ 32. (B) (a) What is meant by 'Chelate effect' ? Give an example. ( $\displaystyle \mathbf{2} \boldsymbol{+} \mathbf{2} \boldsymbol{+} \mathbf{1} \boldsymbol{=} \mathbf{5}$ )
(b)
Write the hybridization and magnetic behaviour of $\displaystyle \left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-}$. (Atomic number : $\displaystyle \mathrm{Fe}=26$ )
(c)
If $\displaystyle \mathrm{PtCl}_{2} \cdot 2 \mathrm{NH}_{3}$ does not react with $\displaystyle \mathrm{AgNO}_{3}$, what will be its formula ?
Marking-scheme solution
(A)
a) The orbital splitting energies are not sufficiently large for forcing paring of electrons.
(b)
In the presence of strong field ligand, d7 is converted into more stable d6
configuration / Strong field effect stabilises higher oxidation state.
(c)
Co-ordination isomerism.
(d)
[Ni(H2O)$\displaystyle 6$]$\displaystyle 2$+ has unpaired electrons whereas [Ni(CN)$\displaystyle 4$]$\displaystyle 2$- has no unpaired electron.
(e)
Pentaamminecarbonatocobalt(III) chloride
(a)
The higher stability of complexes involving chelating ligands as compare to
complexes having non-chelating ligand.
Example: [Co(en)$\displaystyle 3$]$\displaystyle 3$+
(b)
d2sp3 , diamagnetic
(c)
[Pt (NH3)$\displaystyle 2$ Cl2]
Coordination CompoundsBonding in Coordination CompoundsUnderstandlong_answerhard
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CBSE Class 12 Chemistry past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.