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 $C O$ 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. $[ {Fe} ( {H}_2 {O}) _5 {NO}] ^{2+}$Water $( {H}_2 {O})$ 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 $N O$ 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 ( $C O$ ) 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. $[ {Cr}_2( {CO})_{10}] ^{2-}$There are two chromium atoms and all $C O$ ligands are neutral.Let the oxidation number on each ${Cr}$ be $x$. Since the overall charge is $2-$ :$2 x=-2$So, $x=-1$.This matches List II item: III. -1.Thus, the correct matching is:A-II, B-I, C-IV, D-IIIAmong the options given, this corresponds to Option A.