Co-ordination Compounds MCQs for NEET — Chemistry Questions with Answers

Hexafluoroferrate(III) ion, $[FeF_6]^{3-}$, involves iron in the +3 oxidation state. Iron has an electronic configuration of [Ar] 3d^5 4s^1. In the +3 state, it loses three electrons, giving [Ar] 3d^5. Since fluoride is a weak field ligand, it doesn't pair up the electrons, resulting in 5 unpaired electrons.

The compound $[Co(NH_3)_6]Cl_2$ dissociates in water to produce one complex ion $[Co(NH_3)_6]^{2+}$ and two chloride ions $Cl^-$. Thus, it produces a total of 3 ions in solution.

In the complex $Fe(CO)_X$, the value of $X$ is 5, making the complex $Fe(CO)_5$. This is a well-known carbonyl complex of iron.

In the ion $[Cu(H_2O)_4]^{2+}$, the central ion is $Cu^{2+}$. The water molecules act as ligands surrounding the central copper ion.

Ligands are species that donate a pair of electrons to a central metal atom or ion to form a coordination complex. According to Lewis theory, substances that donate electron pairs are called Lewis bases. Therefore, all ligands are Lewis bases.

In the complex $ Ni(CO)_4 $, the nickel metal has a 3d^8 4s^2 electron configuration. When it forms the complex, it uses its 4s and 4p orbitals to hybridize into four $ sp^3 $ orbitals to accommodate the four CO ligands. Therefore, the hybridization in $ Ni(CO)_4 $ is $ sp^3 $.

A ligand must have at least one lone pair of electrons to donate to a central metal atom or ion to form a coordination bond. Therefore, a group of atoms can function as a ligand only when it has an unshared electron pair.

In the complex compound $[Ni(CO)_4]$, the oxidation number of Ni is zero because CO is a neutral ligand. The oxidation state of Ni can be calculated as follows: Let the oxidation state of Ni be x. Since CO is a neutral ligand, its contribution to the overall charge is 0. Therefore, x + 4(0) = 0, which means x = 0.