Chemistry · Coordination compounds · chapter 5 of 10

Class 12 Chemistry Chapter 5: Coordination Compounds MCQs with answers

10 multiple-choice questions on Coordination Compounds, each with its answer and the reason, written from the NCERT chapter. For the CBSE board, JEE Main and NEET, which are set from the same NCERT chapter. Open a question's solution to check your working; then take the free test to find your next chapter.

Question 1
The hexadentate ligand EDTA⁴⁻ binds a metal ion through
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Answer: (c) two N atoms and four O atoms

EDTA⁴⁻ is (⁻OOCCH₂)₂N–CH₂–CH₂–N(CH₂COO⁻)₂: each of the two N atoms and each of the four carboxylate O atoms donates a pair, six in all.

Question 2
Which of the following ligands can bind a metal ion through either of two different donor atoms?
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Answer: (c) SCN⁻

SCN⁻ is ambidentate: it binds through S or through N. Oxalate and ethane-1,2-diamine are didentate, using both donor atoms at once; NH₃ has only N.

Question 3
The coordination number of cobalt in [Co(en)₂(NO₂)Cl]⁺ is
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Answer: (b) 6

Each en is didentate and gives two donor N atoms (2 × 2 = 4); NO₂⁻ and Cl⁻ give one each: 4 + 1 + 1 = 6. Counting ligands instead of donor atoms gives 4.

Question 4
The oxidation state of iron in Na₂[Fe(CN)₅(NH₃)] is
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Answer: (b) +3

Two Na⁺ counter ions make the entity [Fe(CN)₅(NH₃)]²⁻. NH₃ is neutral and each CN⁻ is −1: x + 5(−1) + 0 = −2, so x = +3.

Question 5
Which of the following is a heteroleptic complex?
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Answer: (c) [Co(NH₃)₄(H₂O)Cl]²⁺

A heteroleptic complex has more than one kind of donor group; [Co(NH₃)₄(H₂O)Cl]²⁺ has three (NH₃, H₂O, Cl⁻). The other three carry one kind each and are homoleptic.

Question 6
The IUPAC name of Na₂[Zn(CN)₄] is
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Answer: (d) sodium tetracyanidozincate(II)

The cation is named first. The entity [Zn(CN)₄]²⁻ is an anion, so the metal name ends in -ate; x + 4(−1) = −2 gives Zn(II).

Question 7
The IUPAC name of [Cr(NH₃)₅(NCS)]Cl₂ is
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Answer: (b) pentaamminethiocyanato-N-chromium(III) chloride

M–NCS is bound through N: thiocyanato-N. The entity is a cation, so chromium keeps its name. Two Cl⁻ outside give charge +2: x + 0 + (−1) = +2, x = +3.

Question 8
The formula of diamminebis(ethane-1,2-diamine)cobalt(III) chloride is
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Answer: (c) [Co(NH₃)₂(en)₂]Cl₃

Diammine is two NH₃, bis(ethane-1,2-diamine) two en; all four ligands are neutral, so the cation is [Co(NH₃)₂(en)₂]³⁺ and three Cl⁻ balance it. No chlorido ligand is named, so Cl is not inside the bracket.

Question 9
Platinum(IV) has a secondary valence of 6 in PtCl₄·4NH₃, and all four NH₃ molecules are bound to the metal. One formula unit of the compound gives, in water,
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Answer: (b) 3 ions

Four NH₃ fill four of the six positions, so two Cl⁻ are inside: [Pt(NH₃)₄Cl₂]Cl₂. The two outer Cl⁻ and the complex cation give 3 ions.

Question 10
In the extraction of gold, the metal is dissolved with cyanide in the presence of oxygen and water and then recovered. The complex formed and the metal added to recover gold are
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Answer: (d) [Au(CN)₂]⁻ and zinc

Gold goes into solution as [Au(CN)₂]⁻; adding zinc, the more reactive metal, displaces gold from the complex.

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