Chapter 9 Coordination Compounds

Question 1. Which of the following complexes formed by $Cu^{2+}$ ions is most stable?

(i) $Cu^{2+} + 4NH_3 \rightleftharpoons [Cu(NH_3)_4]^{2+}, \log K = 11.6$

(ii) $Cu^{2+} + 4CN^– \rightleftharpoons [Cu(CN)_4]^{2–}, \log K = 27.3$

(iii) $Cu^{2+} + 2en \rightleftharpoons [Cu(en)_2]^{2+}, \log K = 15.4$

(iv) $Cu^{2+} + 4H_2O \rightleftharpoons [Cu(H_2O)_4]^{2+}, \log K = 8.9$

Question 2. The colour of the coordination compounds depends on the crystal field splitting. What will be the correct order of absorption of wavelength of light in the visible region, for the complexes, $[Co(NH_3)_6]^{3+}$, $[Co(CN)_6]^{3–}$, $[Co(H_2O)_6]^{3+}$

(i) $[Co(CN)_6]^{3–} > [Co(NH_3)_6]^{3+} > [Co(H_2O)_6]^{3+}$

(ii) $[Co(NH_3)_6]^{3+} > [Co(H_2O)_6]^{3+} > [Co(CN)_6]^{3–}$

(iii) $[Co(H_2O)_6]^{3+} > [Co(NH_3)_6]^{3+} > [Co(CN)_6]^{3–}$

(iv) $[Co(CN)_6]^{3–} > [Co(NH_3)_6]^{3+} > [Co(H_2O)_6]^{3+}$

Question 3. When 0.1 mol $CoCl_3(NH_3)_5$ is treated with excess of $AgNO_3$, 0.2 mol of AgCl are obtained. The conductivity of solution will correspond to

(i) 1:3 electrolyte

(ii) 1:2 electrolyte

(iii) 1:1 electrolyte

(iv) 3:1 electrolyte

Question 4. When 1 mol $CrCl_3 \cdot 6H_2O$ is treated with excess of $AgNO_3$, 3 mol of AgCl are obtained. The formula of the complex is :

(i) $[CrCl_3(H_2O)_3] \cdot 3H_2O$

(ii) $[CrCl_2(H_2O)_4]Cl \cdot 2H_2O$

(iii) $[CrCl(H_2O)_5]Cl_2 \cdot H_2O$

(iv) $[Cr(H_2O)_6]Cl_3$

Question 5. The correct IUPAC name of $[Pt(NH_3)_2Cl_2]$ is

(i) Diamminedichloridoplatinum (II)

(ii) Diamminedichloridoplatinum (IV)

(iii) Diamminedichloridoplatinum (0)

(iv) Dichloridodiammineplatinum (IV)

Question 6. The stabilisation of coordination compounds due to chelation is called the chelate effect. Which of the following is the most stable complex species?

(i) $[Fe(CO)_5]$

(ii) $[Fe(CN)_6]^{3–}$

(iii) $[Fe(C_2O_4)_3]^{3–}$

(iv) $[Fe(H_2O)_6]^{3+}$

Question 7. Indicate the complex ion which shows geometrical isomerism.

(i) $[Cr(H_2O)_4Cl_2]^+$

(ii) $[Pt(NH_3)_3 Cl]$

(iii) $[Co(NH_3)_6]^{3+}$

(iv) $[Co(CN)_5(NC)]^{3–}$

Question 8. The CFSE for octahedral $[CoCl_6]^{4–}$ is 18,000 cm$^{–1}$. The CFSE for tetrahedral $[CoCl_4]^{2–}$ will be

(i) 18,000 cm$^{–1}$

(ii) 16,000 cm$^{–1}$

(iii) 8,000 cm$^{–1}$

(iv) 20,000 cm$^{–1}$

Question 9. Due to the presence of ambidentate ligands coordination compounds show isomerism. Palladium complexes of the type $[Pd(C_6H_5)_2(SCN)_2]$ and $[Pd(C_6H_5)_2(NCS)_2]$ are

(i) linkage isomers

(ii) coordination isomers

(iii) ionisation isomers

(iv) geometrical isomers

Question 10. The compounds $[Co(SO_4)(NH_3)_5]Br$ and $[Co(SO_4)(NH_3)_5]Cl$ represent

(i) linkage isomerism

(ii) ionisation isomerism

(iii) coordination isomerism

(iv) no isomerism

Question 11. A chelating agent has two or more than two donor atoms to bind to a single metal ion. Which of the following is not a chelating agent?

(i) thiosulphato

(ii) oxalato

(iii) glycinato

(iv) ethane-1,2-diamine

Question 12. Which of the following species is not expected to be a ligand?

(i) NO

(ii) $NH_4^+$

(iii) $NH_2CH_2CH_2NH_2$

(iv) CO

Question 13. What kind of isomerism exists between $[Cr(H_2O)_6]Cl_3$ (violet) and $[Cr(H_2O)_5Cl]Cl_2 \cdot H_2O$ (greyish-green)?

(i) linkage isomerism

(ii) solvate isomerism

(iii) ionisation isomerism

(iv) coordination isomerism

Question 14. IUPAC name of $[Pt (NH_3)_2 Cl(NO_2)]$ is :

(i) Platinum diaminechloronitrite

(ii) Chloronitrito-N-ammineplatinum (II)

(iii) Diamminechloridonitrito-N-platinum (II)

(iv) Diamminechloronitrito-N-platinate (II)

Question 15. Atomic number of Mn, Fe and Co are 25, 26 and 27 respectively. Which of the following inner orbital octahedral complex ions are diamagnetic?

(i) $[Co(NH_3)_6]^{3+}$

(ii) $[Mn(CN)_6]^{3–}$

(iii) $[Fe(CN)_6]^{4–}$

(iv) $[Fe(CN)_6]^{3–}$

Question 16. Atomic number of Mn, Fe, Co and Ni are 25, 26 27 and 28 respectively. Which of the following outer orbital octahedral complexes have same number of unpaired electrons?

(i) $[MnCl_6]^{3–}$

(ii) $[FeF_6]^{3–}$

(iii) $[CoF_6]^{3–}$

(iv) $[Ni(NH_3)_6]^{2+}$

Question 17. Which of the following options are correct for $[Fe(CN)_6]^{3–}$ complex?

(i) $d^2sp^3$ hybridisation

(ii) $sp^3d^2$ hybridisation

(iii) paramagnetic

(iv) diamagnetic

Question 18. An aqueous pink solution of cobalt(II) chloride changes to deep blue on addition of excess of HCl. This is because____________.

(i) $[Co(H_2O)_6]^{2+}$ is transformed into $[CoCl_6]^{4–}$

(ii) $[Co(H_2O)_6]^{2+}$ is transformed into $[CoCl_4]^{2–}$

(iii) tetrahedral complexes have smaller crystal field splitting than octahedral complexes.

(iv) tetrahedral complexes have larger crystal field splitting than octahedral complex.

Question 19. Which of the following complexes are homoleptic?

(i) $[Co(NH_3)_6]^{3+}$

(ii) $[Co(NH_3)_4 Cl_2]^+$

(iii) $[Ni(CN)_4]^{2–}$

(iv) $[Ni(NH_3)_4Cl_2]$

Question 20. Which of the following complexes are heteroleptic?

(i) $[Cr(NH_3)_6]^{3+}$

(ii) $[Fe(NH_3)_4 Cl_2]^+$

(iii) $[Mn(CN)_6]^{4–}$

(iv) $[Co(NH_3)_4Cl_2]$

Question 21. Identify the optically active compounds from the following :

(i) $[Co(en)_3]^{3+}$

(ii) trans– $[Co(en)_2 Cl_2]^+$

(iii) cis– $[Co(en)_2 Cl_2]^+$

(iv) $[Cr (NH_3)_5Cl]$

Question 22. Identify the correct statements for the behaviour of ethane-1, 2-diamine as a ligand.

(i) It is a neutral ligand.

(ii) It is a didentate ligand.

(iii) It is a chelating ligand.

(iv) It is a unidentate ligand.

Question 23. Which of the following complexes show linkage isomerism?

(i) $[Co(NH_3)_5 (NO_2)]^{2+}$

(ii) $[Co(H_2O)_5CO]^{3+}$

(iii) $[Cr(NH_3)_5 SCN]^{2+}$

(iv) $[Fe(en)_2 Cl_2]^+$

Question 24. Arrange the following complexes in the increasing order of conductivity of their solution: $[Co(NH_3)_3Cl_3]$, $[Co(NH_3)_4Cl_2] Cl$, $[Co(NH_3)_6]Cl_3$, $[Cr(NH_3)_5Cl]Cl_2$

Question 25. A coordination compound $CrCl_3 \cdot 4H_2O$ precipitates silver chloride when treated with silver nitrate. The molar conductance of its solution corresponds to a total of two ions. Write structural formula of the compound and name it.

Question 26. A complex of the type $[M(AA)_2X_2]^{n+}$ is known to be optically active. What does this indicate about the structure of the complex? Give one example of such complex.

Question 27. Magnetic moment of $[MnCl_4]^{2–}$ is 5.92 BM. Explain giving reason.

Question 28. On the basis of crystal field theory explain why Co(III) forms paramagnetic octahedral complex with weak field ligands whereas it forms diamagnetic octahedral complex with strong field ligands.

Question 29. Why are low spin tetrahedral complexes not formed?

Question 30. Give the electronic configuration of the following complexes on the basis of Crystal Field Splitting theory.

$[CoF_6]^{3–}$, $[Fe(CN)_6]^{4–}$ and $[Cu(NH_3)_6]^{2+}$.

Question 31. Explain why $[Fe(H_2O)_6]^{3+}$ has magnetic moment value of 5.92 BM whereas $[Fe(CN)_6]^{3–}$ has a value of only 1.74 BM.

Question 32. Arrange following complex ions in increasing order of crystal field splitting energy ($\Delta_O$) :

$[Cr(Cl)_6]^{3–}, [Cr(CN)_6]^{3–}, [Cr(NH_3)_6]^{3+}$.

Question 33. Why do compounds having similar geometry have different magnetic moment?

Question 34. $CuSO_4 \cdot 5H_2O$ is blue in colour while $CuSO_4$ is colourless. Why?

Question 35. Name the type of isomerism when ambidentate ligands are attached to central metal ion. Give two examples of ambidentate ligands.

Question 36. Match the complex ions given in Column I with the colours given in Column II and assign the correct code :

Code :

(i) A (1) B (2) C (4) D (5)

(ii) A (4) B (3) C (2) D (1)

(iii) A (3) B (2) C (4) D (1)

(iv) A (4) B (1) C (2) D (3)

Question 37. Match the coordination compounds given in Column I with the central metal atoms given in Column II and assign the correct code :

Code :

(i) A (5) B (4) C (1) D (2)

(ii) A (3) B (4) C (5) D (1)

(iii) A (4) B (3) C (2) D (1)

(iv) A (3) B (4) C (1) D (2)

Question 38. Match the complex ions given in Column I with the hybridisation and number of unpaired electrons given in Column II and assign the correct code :

Code :

(i) A (3) B (1) C (5) D (2)

(ii) A (4) B (3) C (2) D (1)

(iii) A (3) B (2) C (4) D (1)

(iv) A (4) B (1) C (2) D (3)

Question 39. Match the complex species given in Column I with the possible isomerism given in Column II and assign the correct code :

Code :

(i) A (1) B (2) C (4) D (5)

(ii) A (4) B (3) C (2) D (1)

(iii) A (4) B (1) C (5) D (3)

(iv) A (4) B (1) C (2) D (3)

Question 40. Match the compounds given in Column I with the oxidation state of cobalt present in it (given in Column II) and assign the correct code.

Code :

(i) A (1) B (2) C (4) D (5)

(ii) A (4) B (3) C (2) D (1)

(iii) A (5) B (1) C (4) D (2)

(iv) A (4) B (1) C (2) D (3)

Question 41. Assertion : Toxic metal ions are removed by the chelating ligands.

Reason : Chelate complexes tend to be more stable.

Question 42. Assertion : $[Cr(H_2O)_6]Cl_2$ and $[Fe(H_2O)_6]Cl_2$ are reducing in nature.

Reason : Unpaired electrons are present in their d-orbitals.

Question 43. Assertion : Linkage isomerism arises in coordination compounds containing ambidentate ligand.

Reason : Ambidentate ligand has two different donor atoms.

Question 44. Assertion : Complexes of $MX_6$ and $MX_5L$ type (X and L are unidentate) do not show geometrical isomerism.

Reason : Geometrical isomerism is not shown by complexes of coordination number 6.

Question 45. Assertion : $[Fe(CN)_6]^{3–}$ ion shows magnetic moment corresponding to two unpaired electrons.

Reason : Because it has $d^2sp^3$ type hybridisation.

Question 46. Using crystal field theory, draw energy level diagram, write electronic configuration of the central metal atom/ion and determine the magnetic moment value in the following :

(i) $[CoF_6]^{3–}$, $[Co(H_2O)_6]^{2+}$, $[Co(CN)_6]^{3–}$

(ii) $[FeF_6]^{3–}$, $[Fe(H_2O)_6]^{2+}$, $[Fe(CN)_6]^{4–}$

Question 47. Using valence bond theory, explain the following in relation to the complexes given below:

$[Mn(CN)_6]^{3–}$ , $[Co(NH_3)_6]^{3+}$, $[Cr(H_2O)_6]^{3+}$ , $[FeCl_6]^{4–}$

(i) Type of hybridisation.

(ii) Inner or outer orbital complex.

(iii) Magnetic behaviour.

(iv) Spin only magnetic moment value.

Question 48. $CoSO_4Cl \cdot 5NH_3$ exists in two isomeric forms ‘A’ and ‘B’. Isomer ‘A’ reacts with $AgNO_3$ to give white precipitate, but does not react with $BaCl_2$. Isomer ‘B’ gives white precipitate with $BaCl_2$ but does not react with $AgNO_3$. Answer the following questions.

(i) Identify ‘A’ and ‘B’ and write their structural formulas.

(ii) Name the type of isomerism involved.

(iii) Give the IUPAC name of ‘A’ and ‘B’.

Question 49. What is the relationship between observed colour of the complex and the wavelength of light absorbed by the complex?

Question 50. Why are different colours observed in octahedral and tetrahedral complexes for the same metal and same ligands?