NEET (UG)

Practice Test 1 — Coordination Compounds

12 questions • 18 minutes • auto-graded with full solutions

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Section A — MCQ (Single Correct & Statement-based)

Question 1

The coordination number of the metal in $[\text{Co(en)}_3]^{3+}$ is:

Solution: Each 'en' is bidentate; 3 × 2 = 6 donor atoms.

Question 2

The oxidation state of Ni in $[\text{Ni(CO)}_4]$ is:

Solution: CO is neutral, complex is neutral, so Ni = 0.

Question 3

EDTA is a ____ ligand.

Solution: EDTA has six donor atoms — hexadentate.

Question 4

Statements: (I) Tetrahedral complexes show cis–trans isomerism. (II) $[\text{Co(en)}_3]^{3+}$ shows optical isomerism. Which is/are correct?

Solution: Tetrahedral shows no cis–trans; only II is correct.

Question 5

$[\text{Fe(CN)}_6]^{4-}$ (strong field) is:

Solution: Strong-field CN⁻ to $d^2sp^3$, low-spin, diamagnetic.

Question 6

In an octahedral complex, the higher-energy $d$-orbital set is:

Solution: $e_g$ is higher in an octahedral field.

Question 7

The colour of coordination compounds is explained by:

Solution: CFT explains colour via $d$–$d$ transitions.

Question 8

The metal present in chlorophyll is:

Solution: Chlorophyll is a magnesium complex.

Section B — Assertion & Reason

Question 9

A: $[\text{Fe(CN)}_6]^{4-}$ is diamagnetic.
R: $\text{CN}^-$ is a strong-field ligand that causes the $d$ electrons of $\text{Fe}^{2+}$ to pair up.

Solution: Strong-field pairing leaves no unpaired electrons — R explains A.

Question 10

A: Crystal field theory can explain the colour of coordination compounds.
R: Ligands split the metal $d$ orbitals, allowing $d$–$d$ electronic transitions in the visible region.

Solution: The $d$–$d$ transition across the splitting gives colour — R explains A.

Question 11

A: Tetrahedral complexes commonly show geometrical (cis–trans) isomerism.
R: All four ligand positions in a tetrahedron are equivalent.

Solution: Tetrahedral complexes do NOT show cis–trans (A false); the four positions are indeed equivalent (R true), which is why.

Question 12

A: In Werner's theory, the secondary valence determines the geometry of a complex.
R: The secondary valence equals the coordination number and is directional/non-ionisable.

Solution: Being the directional coordination number is exactly what fixes the geometry — R explains A.