Chemistry

Coordination Chemistry

319 Questions

Coordination chemistry focuses on coordination compounds, their structures, and their magnetic properties. The questions cover primary and secondary valencies, ligand types, and geometries of complexes. This topic is heavily tested in chemistry competitive exams and requires a good grasp of molecular structures.

primary and secondary valencycomplex geometriesligand field theorymagnetic properties of complexesisomerism in complexes

Coordination Chemistry Questions

Multiple choice

Assertion: In complex [Mn(H2O)6]+2, the d-d transitions are spin allowed. Reason: Each of the d-orbitals of Mn(II) is singly occupied.

There are two statements, Assertion (A) and Reason (R). Consider both the statements independently and mark your answer as under:

1. A and R are both correct and R is the correct explanation of A.
2. A and R are both correct and R is not the correct explanation of A.
3. A is correct and R is incorrect.
4. A is incorrect and R is correct.
5. A and R are both incorrect.

  1. A and R are both correct and R is the correct explanation of A.

  2. A and R are both correct and R is not the correct explanation of A.

  3. A is correct and R is incorrect.

  4. A is incorrect and R is correct.

  5. A and R are both incorrect.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

This option is correct because in case of [Mn(H2O)6]+2, the d-d transitions are spin forbidden because each of the d-orbitals is singly occupied (half filled) and the spin multiplicity changes when the electron goes to an excited state from ground state.

Multiple choice

Which of the following statements is/are false?

  1. The d-d transition band occurs only in visible region.
  2. The position of charge transfer band depends on the nature of metal and ligand.
  3. Frequencies greater than 10,000 cm-1 are not accessible experimentally.

  1. Only 1

  2. Only 2

  3. Only 3

  4. 1 and 3

  5. 2 and 3
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This option is correct because d-d transition band occurs not only in visible but also in near infra-red, ultra-violet regions etc. 

Multiple choice

The ground state term symbol for trivalent niobium ion is

  1. 3F2

  2. 5D0

  3. 2D5/2

  4. 1S0

  5. 4F3/2
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

S = ½ x number of unpaired electrons = ½ x 2 = 1 2S + 1 = 2 x 1 + 1 = 3 L = 3 for d2 ion configuration for which the ground term is F J = L - S = 3 - 1 = 2 The ground state term is (2S + 1)LJ = 3F2 Thus, this option is correct.

Multiple choice

Assertion: Complex [Co(NH3)3F]+2 gives absorption bands in the far ultra-violet region but in complex [Co(NH3)3Br]+2, absorption occurs at a longer wavelength. Reason: These peaks are of low intensity and their extinction coefficients are usually between 1 and 50.

There are two statements, Assertion (A) and Reason (R). Consider both the statements independently and mark your answer as under:

 1. A and R are both correct and R is the correct explanation of A.
2. A and R are both correct and R is not the correct explanation of A.
3. A is correct and R is incorrect.
4. A is incorrect and R is correct.
5. A and R are both incorrect.

  1. A and R are both correct and R is the correct explanation of A.

  2. A and R are both correct and R is not the correct explanation of A.

  3. A is correct and R is incorrect.

  4. A is incorrect and R is correct.

  5. A and R are both incorrect.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Complex [Co(NH3)3F]+2 absorbs in the far ultra-violet region but in complex [Co(NH3)3Br]+2, absorption occurs at a longer wavelength. It is so because the position of the charge transfer band depends on the nature of the metal and the ligand.

Multiple choice

Which of the following statements is/are correct?

  1. The intensity of a spin forbidden transition is about one-hundredth of that of a spin allowed transition.
  2. For d2 configuration, the ground state terms 3F and 3P are considered.
  3. The intense red color of [Fe(SCN)6]+3 ion is due to metal to ligand charge transfer spectra.

  1. Only 1

  2. Only 2

  3. Only 3

  4. 1 and 2

  5. 2 and 3
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

This option is correct because the intensity of spin forbidden transition is about one-hundredth of that for a spin allowed transition and for d2 configuration, the ground state terms 3F and 3P are considered.

Multiple choice

For d-d transition, absorption from electronic excitation always appears as broad bands and not as sharp lines. It is due to which of the following reasons?

  1. Molecular vibrations
  2. Spin orbital coupling 3 John-Teller effect
  3. Laporte forbidden transition

  1. 1 and 2

  2. 2 and 3

  3. 1, 3 and 4

  4. 1, 2 and 3

  5. 2, 3 and 4
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For d-d transition, absorption from electronic excitation always appears as broad bands and not as sharp lines. It is due to molecular vibration, spin orbital coupling and John-Teller effect.

Multiple choice

Match the columns.

 
Transitions Examples
1. d-d transition a. KMnO4
2. Ligand to metal charge transfer b. [Ti(H2O)6]+3
3. Metal to ligand charge transfer c. Ni(CO)4
4. Interligand charge transfer d. [Cu(en)2]+

  1. 1 - d, 2 - c, 3 - a, 4 - b

  2. 1 - c, 2 - b, 3 - d, 4 - a

  3. 1 - b, 2 - a, 3 - c, 4 - d

  4. 1 - b, 2 - a, 3 - d, 4 - c

  5. 1 - a, 2 - b, 3 - c, 4 - d
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This option is correct because [Ti(H2O)6]+3, KMnO4, Ni(CO)4 and [Cu(en)2]+ are examples of d-d transition, ligand to metal charge transfer, metal to ligand charge transfer and interligand charge transfer, respectively.

Multiple choice

Assertion: The mixing of d and p orbitals does not occur in octahedral complexes which have centre of symmetry, like [Ni(NH3)6]+2 and [Co(NH3)6]+3. Reason: In these cases, the metal ligand bonds vibrate so that the ligands spend most of their time out of their centrosymmetric equilibrium position.

There are two statements, Assertion (A) and Reason (R). Consider both the statements independently and mark your answer as under:

1. A and R are both correct and R is the correct explanation of A.
2. A and R are both correct and R is not the correct explanation of A.
3. A is correct and R is incorrect.
4. A is incorrect and R is correct.
5. A and R are both incorrect.

  1. A and R are both correct and R is the correct explanation of A.

  2. A and R are both correct and R is not the correct explanation of A.

  3. A is correct and R is incorrect.

  4. A is incorrect and R is correct.

  5. A and R both are incorrect.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The mixing of d and p orbitals does not occur in octahedral complexes which have centre of symmetry, like [Ni(NH3)6]+2 and [Co(NH3)6]+3, because in these cases, the metal ligand bonds vibrate so that the ligands spend most of their time out of their centrosymmetric equilibrium position. Thus, this option is correct.

Multiple choice

Which of the following statements is/are false?

A. The spin and Laporte forbidden molar absorption coefficients are very low. B. Multiplicity forbidden transition bands are sharp while multiplicity allowed transition yields broad bands. C. Substitution in octahedral complexes, which destroys the centre of symmetry of the ligand, gives weak absorption.

  1. Only A

  2. Only B

  3. Only C

  4. A and B

  5. B and C
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Substitution in octahedral complexes, which destroys the center of symmetry of the ligand, gives higher absorption.

Multiple choice

Which one of the following salts is called fischer salt?

  1. K3[Co(NO2)6]

  2. K4[NO(SO3)2]

  3. K3[Fe(CN)6]

  4. [Pt2(NH3)4Cl4]

  5. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This option is correct because this complex is called as fischer salt. It is a yellow powder which decomposes at melting point 200 0C and used in medicine as yellow pigment.

Multiple choice

The complex [CuSO4.Cu(OH)2] is called as

  1. basic copper carbonate

  2. bronchanite

  3. microcosmic salt

  4. nitre cake

  5. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This option is correct because when sulphur dioxide is present in the air, a layer of basic sulphate is formed and it is called as bronchanite.

Multiple choice

Which of the following d-electronic configurations in an octahedral complex will give maximum CFSE?

  1. Low spin-d4

  2. High spin-d4

  3. Low spin-d5

  4. High spin-d5

  5. High spin-d7
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In octahedral complexes, CFSE is given by the formula: CFSE = value of t2g (n) + value of eg (n) Dq, Now, CFSE for low-spin d4 = -4 (4) + 6 (0) = -16 + 0 = -16 Dq CFSE for high-spin d4 = -4 (3) + 6 (1) = -12 + 6 = -6 Dq CFSE for low-spin d5 = -4 (5) + 6 (0) = -20 + 0 = -20 Dq CFSE for high-spin d5 = -4 (3) + 6 (2) = -12 + 12 = 0 Dq CFSE for low-spin d7 = -4 (5) + 6 (2) = -20 + 12 = -8 Dq Hence, low-spin d5 will give maximum CFSE in an octahedral complex.

Multiple choice

Which metal ion represents zero value of CFSE, if it is associated with weak field ligand?

  1. Fe3+

  2. Fe2+

  3. Cr2+

  4. Mn+

  5. Mn3+
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In a weak field ligand, the filling of electrons is in accordance with Hund’s rule. The CFSE is given by the formula  CFSE = value of t2g (n) + value of eg (n) Dq, Fe3+ corresponds to the d5 configuration. Now, CFSE for Fe3+ (d5) = - 4 (3) + 6 (2) = - 12 + 12 = 0 Dq CFSE for Fe2+ (d6) = - 4 (4) + 6 (2) = - 16 + 12 = - 4 Dq CFSE for Cr2+ (d4) = - 4 (3) + 6 (1) = - 12 + 6 = - 6 Dq CFSE for Mn+ (d6) = - 4 (4) + 6 (2) = - 16 + 12 = - 4 Dq CFSE for Mn3+ (d4) = - 4 (3) + 6 (1) = - 12 + 6 = - 6 Dq Hence, the metal ion with zero CFSE is Fe3+ when it is associated with weak field ligand.

Multiple choice

Which of the following compound has 4.9 BM magnetic moment?

  1. Hg[Co(CNS)4]+

  2. [Fe(diph)3]+++

  3. K3[Cr(CNS)6]

  4. [MnBr4]2-

  5. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This option is correct, because the octahedral complex of the Co possess the magnetic moment 4.9 BM. It would be concluded that the Co is in a bivalent state and occupies 3d7 and the bonding is free spin types, corresponding to n = 3.