KCET 2026 Chemistry Solved Paper

Concept:Match each complex with its geometry based on coordination number and ligand field strength.Explanation:For $\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+}$, the coordination number is $6$.Complexes with coordination number $6$ adopt octahedral geometry.So, $(a) \rightarrow (ii)$.For $\left[\mathrm{NiCl}_{4}\right]^{2-}$, nickel is in $+2$ oxidation state, giving a $d^8$ configuration.Since $\mathrm{Cl}^-$ is a weak field ligand, pairing does not occur and the geometry is tetrahedral.So, $(b) \rightarrow (iii)$.For $\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}$, nickel is again $+2$ with a $d^8$ configuration.But $\mathrm{CN}^-$ is a strong field ligand, causing pairing and giving square planar geometry.So, $(c) \rightarrow (iv)$.For $\left[\mathrm{Fe}(\mathrm{CO})_{5}\right]$, the coordination number is $5$.A coordination number of $5$ with $\mathrm{CO}$ ligands gives trigonal bipyramidal geometry.So, $(d) \rightarrow (i)$.Thus, the correct matching is:$a \rightarrow ii, \quad b \rightarrow iii, \quad c \rightarrow iv, \quad d \rightarrow i$.Answer:Option A is correct.