Class 12 Coordination Compounds Mock Test (CBSE)

Topics in Coordination Compounds

• Werner's theory of coordination compounds
• Definitions of important terms
• Nomenclature of coordination compounds
• Isomerism in coordination compounds
• Valence bond theory
• Magnetic properties of coordination compounds
• Crystal field theory
• Colour in coordination compounds
• Importance and applications of coordination compounds

Coordination Compounds practice questions with answers

1. Q1Multiple choice·1 mark
   How many geometrical isomers are possible for the octahedral complex $[\text{Co}(\text{NH}_3)_3\text{Cl}_3]$?

   1. (a)1
   2. (b)2
   3. (c)3
   4. (d)4
   Show answer and step marks

   1. Correct option: (b) 2 (the facial and meridional isomers)+1

   Answer: (b)
2. Q2Multiple choice·1 mark
   A student records the compound $[Cr(H_2O)_4Cl_2]Cl$ in a lab notebook. Which is its correct IUPAC name?

   1. (a)tetrachloridodiaquachromium(III) chloride
   2. (b)tetraaquadichlorochromium(III) chloride
   3. (c)tetraaquadichloridochromium(II) chloride
   4. (d)tetraaquadichloridochromium(III) chloride
   Show answer and step marks

   1. Correct option: (d) tetraaquadichloridochromium(III) chloride+1

   Answer: (d)
3. Q3Assertion and reason·1 mark
   Assertion (A): Linkage isomers $[\text{Co}(\text{NH}_3)_5(\text{NO}_2)]\text{Cl}_2$ and $[\text{Co}(\text{NH}_3)_5(\text{ONO})]\text{Cl}_2$ differ in their properties. Reason (R): Linkage isomerism occurs when the same ligands are bonded to the metal through the same donor atom.

   1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
   2. (b)Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).
   3. (c)Assertion (A) is true but Reason (R) is false.
   4. (d)Assertion (A) is false but Reason (R) is true.
   Show answer and step marks

   1. Correct option: (c) Assertion (A) is true but Reason (R) is false (linkage isomers arise when an ambidentate ligand binds through different donor atoms)+1

   Answer: (c)
4. Q4Assertion and reason·1 mark
   Assertion (A): In an octahedral crystal field, the $d_{x^2-y^2}$ and $d_{z^2}$ orbitals experience higher electrostatic repulsion and have higher energy than the $t_{2g}$ set. Reason (R): The $e_g$ orbitals point directly towards the axes along which the ligands approach the metal ion in an octahedral geometry.

   1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
   2. (b)Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).
   3. (c)Assertion (A) is true but Reason (R) is false.
   4. (d)Assertion (A) is false but Reason (R) is true.
   Show answer and step marks

   1. Correct option: (a)+1

   Answer: (a)
5. Q5Short answer·2 marks
   A coordination compound has the formula $\text{PtCl}_4 \cdot 4\text{NH}_3$. When one mole of this compound is treated with excess silver nitrate solution, two moles of $\text{AgCl}$ are precipitated. Based on Werner's coordination theory, write the structural formula of the compound and state the number of ions furnished by one formula unit of the compound in aqueous solution.
   Show answer and step marks

   1. Since $1\text{ mole}$ of the compound gives $2\text{ moles}$ of $\text{AgCl}$ precipitate, two chloride ions are present outside the coordination sphere. Structural formula: $\text{[Pt(NH}_3\text{)}_4\text{Cl}_2\text{]Cl}_2$.+1
   2. In aqueous solution, each formula unit dissociates into $1$ complex cation $[\text{Pt(NH}_3\text{)}_4\text{Cl}_2]^{2+}$ and $2$ chloride anions, a total of $3$ ions (so one mole gives $3$ moles of ions).+1

   Answer: Structural formula: $\text{[Pt(NH}_3\text{)}_4\text{Cl}_2\text{]Cl}_2$; $3$ ions per formula unit ($3$ moles of ions per mole).
6. Q6Long answer·5 marks
   At the annual village fair, a stall owner silver-plates brass key chains. The electroplating bath is prepared by dissolving $K[Ag(CN)_2]$ in water, and the item to be plated is connected as the cathode. Answer the following. (i) Calculate the oxidation number of silver in the complex ion $[Ag(CN)_2]^-$. [1] (ii) Explain why the cyanide ion, $CN^-$, can act as a ligand towards the silver ion in this complex. [2] (iii) State the coordination number of silver in $[Ag(CN)_2]^-$. [1] (iv) Explain why the potassium ion is written outside the square bracket in $K[Ag(CN)_2]$. [1]
   Show answer and step marks

   1. (i) Let the oxidation number of Ag be $x$; then $x + 2(-1) = -1$, so $x = +1$.+1
   2. (ii) The cyanide ion has a lone pair on its carbon atom, which it can donate to the silver ion.+1
   3. The donation forms a coordinate bond with silver, so $CN^-$ is a ligand that donates an electron pair to the metal ion.+1
   4. (iii) Two $CN^-$ ligands are bonded to silver, so the coordination number is 2.+1
   5. (iv) $K^+$ is not bonded to silver; it is a counter ion held outside the coordination sphere by electrostatic attraction.+1

   Answer: (i) Oxidation number of Ag = +1. (ii) CN$^-$ donates a lone pair from carbon to Ag$^+$ through a coordinate bond. (iii) Coordination number = 2. (iv) K$^+$ is a counter ion outside the coordination sphere, not bonded to silver.

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