BITSAT 2024 Shift 1 Paper

Let's determine the oxidation number of the metal in each complex step by step.
For A. Ni(CO)4
Each CO ligand is neutral.
The overall complex is neutral.
Therefore, the oxidation number on Ni is 0 .
This matches List II item: II. Zero.
For B. [Fe(H2O)5‌NO]2+
Water (H2O) is neutral.
In many nitrosyl complexes, when the NO ligand binds linearly, it is considered to act as NO+(nitrosonium).
If we assign +1 to the NO ligand, let the oxidation state of Fe be x :
x+(+1)=+2
So, x=+1.
This matches List II item: I. +1.
For C.[Co(CO)5]2−
Again, all carbonyl ( CO ) ligands are neutral.
The overall complex carries a charge of 2-.
Hence, the oxidation number on Co is -2 .

This matches List II item: IV. -2.
For D. [Cr2(CO)10]2−
There are two chromium atoms and all CO ligands are neutral.
Let the oxidation number on each Cr be x. Since the overall charge is 2− :
2x=−2
So, x=−1.
This matches List II item: III. -1.
Thus, the correct matching is:
A-II, B-I, C-IV, D-III
Among the options given, this corresponds to Option A.