CBSE 2024 · Region 5 · Set 1 · Q29 · 4 marks
The oxidation number of the central atom in a complex is defined as the charge it would carry if all the ligands are removed along with the electron pairs that are shared with the central atom. Similarly the charge on the complex is the sum of the charges of the constituent parts i.e. the sum of the charges on the central metal ion and its surrounding ligands. Based on this, the complex is called neutral if the sum of the charges of the constituents is equal to zero. However, for an anion or cationic complex, the sum of the charges of the constituents is equal to the charge on the coordination sphere. Based on the above information, answer the following questions :(a)Define ambidentate ligand with an example.(b)What type of isomerism is shown by $\displaystyle \left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right] \mathrm{SO}_{4}$ and $\displaystyle \left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{SO}_{4}\right] \mathrm{C} l$ ?Define Chelate effect. How it affects the stability of complex ?Find the coordination number and oxidation state of chromium in $\displaystyle \mathrm{Na}_{3}\left[\mathrm{Cr}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]$.
The oxidation number of the central atom in a complex is defined as the charge it would carry if all the ligands are removed along with the electron pairs that are shared with the central atom. Similarly the charge on the complex is the sum of the charges of the constituent parts i.e. the sum of the charges on the central metal ion and its surrounding ligands. Based on this, the complex is called neutral if the sum of the charges of the constituents is equal to zero. However, for an anion or cationic complex, the sum of the charges of the constituents is equal to the charge on the coordination sphere. Based on the above information, answer the following questions :
(a)
Define ambidentate ligand with an example.
(b)
What type of isomerism is shown by $\displaystyle \left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right] \mathrm{SO}_{4}$ and $\displaystyle \left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{SO}_{4}\right] \mathrm{C} l$ ?
Define Chelate effect. How it affects the stability of complex ?
Find the coordination number and oxidation state of chromium in $\displaystyle \mathrm{Na}_{3}\left[\mathrm{Cr}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]$.
Marking-scheme solution
(a)
Ligand which has two different donor atoms and either of the two ligates in the complex. Examples :- \(\displaystyle \mathrm{NO}_{2}{ }^{-} / \mathrm{SCN}^{-} / \mathrm{CN}^{-}\)
(b)
Ionization isomerism
When a bi-dentate or polydentate ligand ligates to the metal atom or ion that forms a ring. More is the chelation more is the stability.
Coordination number: $\displaystyle 6$ Oxidation state : +$\displaystyle 3$
Coordination CompoundsDefinitions of Some Important Terms Pertaining to Coordination CompoundsApplycase_studymedium
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CBSE Class 12 Chemistry past-paper question from the 2024board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.