MCQs on Polarisation and Fajans Rule

When the cation approaches the anion the net positive charge on the cation attracts the electron cloud of the anion and repels the positively charged nucleus of the anion. Therefore, the electron cloud of the anion gets distorted or bulged towards the cation. This is called polarization of the anion. The power of the cation to distort the anion is known as the polarising power of the cation and the tendency of an anion to get polarised is called polarisability of the anion. In inorganic chemistry, Fajans rule formulated by Kazimierz Fajans was used to predict whether a chemical bond will be covalent or ionic, which depends on the charge on the cation and the relative sizes of the cation and anion.

1. The molecule, which contains sp3d2 and p orbitals overlapping in it is

  1. PCl5
  2. BrF5
  3. ClF3
  4. IF7

Answer: (b)

2. Homolytic fission of C-C bond of ethane (C2H6) which gives an intermediate in which carbon atom is

  1. sp3 hybridised
  2. sp2 hybridised
  3. sp hybridised
  4. sp3d hybridised

Answer: (b)

3. Which of the following compounds has the electron pair geometry as trigonal bipyramidal with three equatorial positions occupied by lone pairs of electrons?

  1. AlCl3
  2. XeF2
  3. Pt(NH3)2Cl
  4. CH3MgBr

Answer: (b)

4. Select correct statement

  1. Cations with 18 electron shells have greater polarising power than the cations with 8-electron shells.
  2. Inner shell electrons have a poor shielding effect on the nucleus and thus electronegativity of the 18 electron shell is increased.
  3. CuCl is covalent and NaCl is ionic
  4. All are correct statements

Answer: (d)

5. In BrF3 molecule the lone pairs occupy an equatorial position to minimise

  1. lone pair-bond pair repulsion only
  2. bond pair-bond pair repulsion only
  3. lone pair-lone pair repulsion and lone pair-bond pair repulsion
  4. lone pair-lone pair repulsion only

Answer: (d)

6. The hybridisation of phosphorous in POCl3 is the same as in

  1. P in PCl3
  2. S in SF4
  3. Cl in ClF3
  4. B in BCl3

Answer: (a)

7. If the bond length and dipole moment of diatomic molecules are 1.25Ao and 1.0D respectively, what is the percent ionic character of the bond?

  1. 10.66
  2. 12.35
  3. 16.66
  4. 19.33

Answer: (c)

8. The molecule MLx is planar with six pairs of electrons around M in the valence shell. The value of x is

  1. 6
  2. 2
  3. 4
  4. 3

Answer: (c)

9. Total number of electron pairs in PCl5, PCl4+ and PCl6 are respectively

  1. 20, 16, 24
  2. 24, 16, 20
  3. 16, 20, 24
  4. 24, 20, 16

Answer: (a)

10. If the water molecule is linear

  1. it would have a very high boiling point
  2. it would be highly reactive
  3. its dipole moment would be zero
  4. it would be highly ionic

Answer: (c)

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