15 extra multiple-choice questions for Coordination Chemistry (12th Standard Chemistry, Samacheer Kalvi), beyond the ones printed in the textbook — each with the correct option highlighted and a clear, worked explanation. Free to read in English and Tamil.
Q1
Which of the following observations correctly distinguishes a double salt from a coordination compound in aqueous solution?
- A. A double salt dissociates into its constituent simple ions and loses its identity.Correct
- B. A coordination compound dissociates completely into simple cations and anions.
- C. A double salt retains the identity of the complex ion in solution.
- D. Both types of compounds behave identically when dissolved in water.
Explanation. According to the sources, double salts like Mohr's salt dissociate into their constituent simple ions in solution, whereas the complex ion in a coordination compound does not lose its identity and never dissociates to give simple ions.
Q2
According to Werner's theory, which type of valence is non-ionisable and corresponds to the coordination number of the metal?
- A. Primary valence
- B. Secondary valenceCorrect
- C. Tertiary valence
- D. Ionic valence
Explanation. Werner's theory states that secondary valence is non-ionisable, directional, and satisfied by ligands in the inner coordination sphere. In modern terminology, it refers to the coordination number.
Q3
In the coordination entity \([Fe(CN)_6]^{4-}\), the central metal ion \(Fe^{2+}\) acts as a:
- A. Lewis base
- B. Bronsted acid
- C. Lewis acidCorrect
- D. Reducing agent
Explanation. The central metal ion has the ability to accept electron pairs from ligands, which makes it a Lewis acid.
Q4
What is the coordination number of \(Ni^{2+}\) in the complex \([Ni(en)_3]Cl_2\), where 'en' stands for ethane-1,2-diamine?
- A. 3
- B. 2
- C. 4
- D. 6Correct
Explanation. Ethane-1,2-diamine is a bidentate ligand containing two donor nitrogen atoms. Since there are three such ligands, the total number of coordination bonds (coordination number) is \(3 \times 2 = 6\).
Q5
Based on IUPAC guidelines, what is the correct name for the complex \([Ag(NH_3)_2]Cl\)?
- A. Diamminesilver(I) chlorideCorrect
- B. Silver diamine chloride
- C. Diamminesergentate(I) chloride
- D. Diamine silver(II) chloride
Explanation. The cation is named first (diamminesilver(I)) followed by the anion (chloride). The oxidation state of silver is +1.
Q6
Which suffix is used for the central metal atom in a coordination compound where the complex ion carries a net negative charge?
- A. -ite
- B. -ide
- C. -ateCorrect
- D. -ium
Explanation. According to IUPAC nomenclature rules, for anionic complexes, the suffix '-ate' is added to the name of the central metal.
Q7
Linkage isomerism arises in coordination compounds containing which type of ligand?
- A. Unidentate ligands
- B. Ambidentate ligandsCorrect
- C. Chelating ligands
- D. Bridging ligands
Explanation. Linkage isomerism occurs when an ambidentate ligand can coordinate to the central metal atom through two different donor atoms (e.g., \(NO_2^-\) through N or O).
Q8
The compounds \([Pt(en)_2Cl_2]Br_2\) and \([Pt(en)_2Br_2]Cl_2\) are examples of:
- A. Coordination isomers
- B. Hydration isomers
- C. Ionisation isomersCorrect
- D. Linkage isomers
Explanation. Ionisation isomers result from the exchange of an ionisable counter ion with a ligand in the coordination entity, yielding different ions in solution.
Q9
In Valence Bond Theory (VBT), a complex with \(sp^3\) hybridisation will have which geometry?
- A. Square planar
- B. Octahedral
- C. TetrahedralCorrect
- D. Linear
Explanation. As per the sources, a coordination number of 4 with \(sp^3\) hybridisation corresponds to a tetrahedral geometry.
Q10
Which of the following ligands is considered a 'strong field ligand' capable of causing pairing of electrons in the central metal atom?
- A. \(Cl^-\)
- B. \(F^-\)
- C. \(CO\)Correct
- D. \(Br^-\)
Explanation. According to the spectrochemical series and VBT assumptions, ligands like \(CO\) and \(CN^-\) are strong field ligands that cause pairing of electrons.
Q11
In an octahedral crystal field, the five degenerate d-orbitals split into which two sets of orbitals?
- A. \(t_2\) and \(e\)
- B. \(t_{2g}\) and \(e_g\)Correct
- C. \(s\) and \(p\)
- D. \(d_{xy}\) and \(d_{z^2}\)
Explanation. Crystal Field Theory (CFT) explains that in an octahedral field, the d-orbitals split into the lower energy \(t_{2g}\) set and the higher energy \(e_g\) set.
Q12
Why are complexes of \(Zn^{2+}\) (with \(d^{10}\) configuration) generally colourless?
- A. They absorb all wavelengths of visible light.
- B. The d-d transition is not possible because the d-orbitals are completely filled.Correct
- C. They do not have a coordination sphere.
- D. The crystal field splitting energy is too high.
Explanation. The observed colour of coordination compounds is due to d-d transitions. In \(d^{10}\) ions like \(Zn^{2+}\), there are no vacant d-orbitals to allow for such transitions, making them colourless.
Q13
In metal carbonyls, the synergic effect that accounts for the strong M-CO bond is due to:
- A. Only sigma bond formation
- B. Only pi-back bonding
- C. Both sigma donation from ligand and pi-back bonding from metalCorrect
- D. Electrostatic attraction between ions
Explanation. The sources describe the bonding in metal carbonyls as involving electron donation from CO to the metal (sigma bond) and simultaneous back-donation from the metal to CO (pi-back bonding), which strengthens the bond synergistically.
Q14
Which of the following terms refers to the free energy change (\(\Delta G\)) of a complex formation reaction?
- A. Kinetic stability
- B. Thermodynamic stabilityCorrect
- C. Labile nature
- D. Inert nature
Explanation. Thermodynamic stability refers to the extent to which a complex will form from or be transformed into another species at equilibrium, specifically related to \(\Delta G\).
Q15
Which essential vitamin is a coordination compound of cobalt?
- A. Vitamin A
- B. Vitamin B12Correct
- C. Vitamin C
- D. Vitamin D
Explanation. The sources identify Vitamin B12 (cobalamine) as an essential vitamin that is a coordination compound of cobalt.
