Chemical Bonding and Molecular Structure

Q1. Kossel and Lewis approach was based on the:

  1. Reactivity of elements.
  2. Inertness of noble gases.
  3. Reactivity of metals.
  4. Inertness of non-metals.
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Ans: 2. Inertness of noble gases.

Q2. Which of the following methods can be used for the formation of bond in homonuclear diatomic hydrogen 1
molecule?

  1. Non-linear combination of atomic orbitals.
  2. Linear combination of atomic orbitals.
  3. Linear combination of molecular orbitals.
  4. None of the above.
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Ans: 2. Linear combination of atomic orbitals.

Q3. The shape of a molecule depends on:

  1. Number of bonded valence electron pairs.
  2. Number of non-bonded valence electron pairs.
  3. All the electrons.
  4. ‘a’ and ‘b’ above.
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Ans: 4. ‘a’ and ‘b’ above.

Explanation:
The shape of a molecule depends upon valence electron pairs i.e. both bonded and non-bonded.

Q4. The decreasing order of the repulsive interaction of electron pairs is (Here, lp = lone pair, bp = bond pair):

  1. lp-lp > lp-bp > bp-bp.
  2. lp-bp > lp-lp > bp-bp.
  3. lp-lp > bp-bp > lp-bp.
  4. bp-bp > lp-lp > lp-bp.
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Ans: 1. lp-lp > lp-bp > bp-bp.

Explanation:
According to VSEPR theory, the repulsive interaction of electron pairs decrease in the order.
Lone pair (lp) – lone pair (lp) > lone pair (lp) – bond pair (bp) > bond pair (bp) – bond pair (bp).

Q5. The product of the magnitude of the charge and the distance between the centres of positive and negative
charge is called:

  1. Charge ratio.
  2. Dipole moment.
  3. Current flow.
  4. Magnetic moment.
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Ans: 2. Dipole moment.

Explanation:
As a result of polarisation, the molecule possesses the dipole moment which can be defined as the product of magnitude of the
charge and the distance between the centres of positive and negative charge.

Q6. In case of bonding molecular orbital the electron density is located:

  1. Away from the space between nuclei of the bonded atom.
  2. Between the nuclei of the bonded atoms.
  3. In the outer shell.
  4. In the inner orbital.
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Ans: 2. Between the nuclei of the bonded atoms.

Explanation:
In case of bonding molecular orbital the electron density is located between the nuclei of the bonded atoms.

Q7. The valence bond theory explains the shape, the formation and directional properties of bonds in polyatomic
molecules like CH , NH and H O etc, in terms of:

  1. Overlapping of atomic orbitals.
  2. Hybridisation of atomic orbitals.
  3. Both (a) and (b).
  4. None of the above.
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Ans: 1. Both (a) and (b).

Explanation:
The valence bond theory explains the shape, the formation and directional properties of bonds in polyatomic molecules like CH , NH
and H O etc., in terms of overlap and hybridisation of atomic orbitals.

Q8. VBT theory is based on the:

  1. Knowledge of atomic orbitals and electronic configuration of elements.
  2. Overlapping criteria and the hybridisation of atomic orbitals.
  3. The principles of variation and superposition.
  4. All of the above.
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Ans: 4. All of the above.
Explanation:
VBT is based on all the given criteria.

Q9. The bond formed, as a result of the electrostatic attraction between the positive and negative ions was termed
as:

  1. Electrovalent bond.
  2. Covalent bond.
  3. Coordinate bond.
  4. None of these.
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Ans: 1. Electrovalent bond.

Q10. The amount of energy required to break one mole of bonds of a particular type between two atoms in a gaseous
state is called:

  1. Bond enthalpy.
  2. Bond angle.
  3. Bond order.
  4. None of these.
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Ans: 1. Bond enthalpy.

Explanation:
Bond enthalpy is the amount of energy required to break one mole of bonds of a particular type between two atoms in a gaseous
state.

    Q23. Lewis approach helps in writing the structure of molecules but it fails to explain:

    1. The formation of chemical bond.
    2. The reason for the difference in bond dissociation enthalpies and bond lengths in molecule like H , F etc.
    3. The idea about the shapes of polyatomic molecules.
    4. All of the above.
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    Ans: 4. All of the above.

    Q11. The structure which represents the molecular structure more accurately is called:

    1. Resonance hybrid.
    2. Canonical structure.
    3. Resonating structure.
    4. None of these.
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    Ans: 1. Resonance hybrid.

    Q12. If internuclear axis is taken to be in z-direction then, which of the following orbital does form bond?
    Choose the correct option:

    1. Px orbitals.
    2. Py orbitals.
    3. Pz orbitals.
    4. All of these.
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    Ans: 3. P orbitals.

    Explanation:
    In such a condition only Pz orbitals form bond along the z-axis while Px and Py form bonds.

    Q13. Which of the following statements are correct about CO32-?

    1. The hybridization of central atom is sp3 .
    2. Its resonance structure has one C – O single bond and two C = O double bonds.
    3. The average formal charge on each oxygen atom is 0.67 units.
    4. All C – O bond lengths are equal.
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    Ans: 3. The average formal charge on each oxygen atom is 0.67 units.

    Q14. The formation of hydrogen molecule takes place when:

    1. The energy state is minimum.
    2. Two hydrogen atomic orbitals undergo large extent of overlapping.
    3. Both (a) and (b).
    4. None of the above.
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    Ans: 3. Both (a) and (b).

    Q15. Ionic bonds will be formed more easily between elements with comparatively:

    1. Low ionisation enthalpy and high electron affinity.
    2. High ionisation enthalpy and high electron affinity.
    3. Low ionisation enthalpy and low electron affinity.
    4. High ionisation enthalpy and low electron affinity.
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    Ans: 1. Low ionisation enthalpy and high electron affinity.

    Explanation:
    Lonic bonds will be formed more easily between elements with comparatively low ionisation enthalpies and high negative value of
    electron gain enthalpy.

    Q16. The group valence of the element is generally equal to the:

    1. Number of dots in Lewis symbol.
    2. Eight minus the number of dots.
    3. Valence electrons.
    4. Any of the above may possible.
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    Ans: 4. Any of the above may possible.

    Explanation:

    The group valence of the elements is generally equal to either the number of dots in Lewis symbols or eight minus the number of
    dots or valence electrons.

    Q17. expressed as wave function can represent:

    1. Probability of an electron.
    2. Amplitude of the electron waves.
    3. Electron wave function.
    4. Both (a) and (c).
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    Ans: 2. Amplitude of the electron waves.

    Q18. Which of the following angle corresponds to sp hybridisation?

    1. 90º
    2. 120°
    3. 180°
    4. 109°
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    Ans: 2. 120°

    Explanation:
    sp hybridisation gives three sp hybrid orbitals which are planar triangular forming an angle of 120° with each other.
    The electronic configurations of three elements A, B and C are given below.

    Q19. Lewis has pictured the atom in terms of kernel and the outermost shell that could accommodate a maximum of:

    1. 6 electrons.
    2. 10 electrons.
    3. 8 electrons.
    4. 2 electrons.
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    Ans: 3. 8 electrons.

    Q20. The molecular formula of the compound formed from B and C will be:

    1. BC
    2. B2C
    3. BC2
    4. BC3
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    Ans: 4. BC

    Explanation:
    B represent P and C represents Cl. The stable compound is PCl i.e., BC .

    Q21. Which of the following molecule does not show hydrogen bonding?

    1. HF
    2. H2O
    3. NH3
    4. H S
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    Ans: 4. H S
    Explanation:
    H S does not show hydrogen bonding also, that’s why it exists as a gas.

    Q22. The condition to form a molecular orbital from atomic orbitals is:

    1. Atomic orbitals must have comparable energies and of proper symmetry.
    2. Only atomic orbitals must be in proper symmetry.
    3. Only atomic orbitals must be of comparable energies.
    4. None of the above.
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    Ans: 1. Atomic orbitals must have comparable energies and of proper symmetry.

    Explanation:

    According to molecular orbital theory (MOT), the atomic orbitals of comparable energies and proper symmetry combine to form
    molecular orbitals.

    Q23. Which of the following molecules is expected to be diamagnetic?

    1. S2
    2. B2
    3. N2
    4. O2
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    Ans: 3. N2

    Q24. In which of the following molecules molecular orbital is filled after and molecular orbitals?

    1. O2
    2. Ne2
    3. N2
    4. F2
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    Ans: 2. N2

    Q25. In the formation of bonding molecular orbital, the two electrons waves of the bonding atoms reinforce each
    other due to:

    1. Constructive interference.
    2. Destructive interference.
    3. Both (a) and (b).
    4. None of the above.
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    Ans: 1. Constructive interference.

    Q26. According to Pauling, the atomic orbitals combine to form new set of equivalent atomic orbitals known as:

    1. Molecular orbitals.
    2. Hybrid orbitals.
    3. Pure orbitals.
    4. None of these.
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    Ans: 2. Hybrid orbitals.

    Explanation:


    According to Pauling the atomic orbitals combine to form new set of equivalent orbitals known as hybrid orbitals. Unlike pure orbitals,
    the hybrid orbitals are used in bond formation.

    Q27. The electron probability distribution around a group of nuclei in a molecule is given by:

    1. Atomic orbital.
    2. Molecular orbital.
    3. Antibonding molecular orbital.
    4. None of the above.
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    Ans: 2. Molecular orbital.

    Explanation:
    The electron probability distribution around a group of nuclei in a molecule is given by a molecular orbital.

    Q28. Which of the following statements are not correct?

    1. NaCl being an ionic compound is a good conductor of electricity in the solid state.
    2. In canonical structures there is a difference in the arrangement of atoms.
    3. Hybrid orbitals form stronger bonds than pure orbitals.
    4. Vsepr theory can explain the square planar geometry of XeF4
    Click To View The Answer

    Ans: 1. NaCl being an ionic compound is a good conductor of electricity in the solid state.

    Q29. Which of the following compounds shows the presence of intramolecular H-bond?

    1. H2O2
    2. HCN
    3. Cellulose
    4. Conc. Acetic acid
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    Ans: 3. Cellulose.

    Explanation:
    Cellulose has intramolecular H-bonding.

    Q30. Which theory can be best understood by considering the formation of the chlorine molecule, Cl2 ?

    1. Lewis theory.
    2. Langmuir theory.
    3. Lewis-Langmuir theory.
    4. Kossel-Lewis theory.
    Click To View The Answer

    Ans: 3. Lewis-Langmuir theory.