Important MCQs on Chemical Bonding and Molecular Structure

Ans. (B) Van-der Waal’s attraction 

Explanation: The molecules in a crystal, are held together, through Vander Waal's force of attraction. The atoms in covalent molecules are held together by strong covalent bonds, however, there are only weak forces of attraction between molecules. These weak forces of attraction between molecules are referred to as Vander Waal's force of interest and can be broken with little energy. 

Ans. (A) low ionization enthalpy and high electron affinity

Explanation: Ionic bonds will be formed more easily between elements with low ionization enthalpy and elements with a comparatively high negative value of electron gain enthalpy. Ionization enthalpy refers to the energy required to remove the electron from the outermost shell while electron gain enthalpy is the energy released when an atom gains an electron. The formation of an ionic bond is dependent on both these factors. Easy formation of anion and cation will lead to the formation of ionic compounds easily. 

Ans. (B) Water

Explanation: Dipole moment is the measurement of the bond polarity. Water has a dipole moment of more than 0. It is due to the presence of oxygen which has a partial negative charge and the presence of hydrogen which has a partial positive charge and this charge separation results in the dipole moment of water as zero. The dipole moment of water = 1.84 D.

Ans. (B) BF₃

Explanation: BF₃ has trigonal planar geometry. The hybridization of BF₃ is sp2 hybridization. The central atom B has 3 bond pairs and zero lone pairs of electrons. Hence it undergoes sp2 hybridization. Option ‘d’ has the T-shaped geometry and option ‘a’ and ‘c’ have pyramidal-shaped geometry. 

Ans. (D) octahedral geometry

Explanation: Since the hybridization of central metal in [Co(NH₃)₆³⁺] complex ion is Sp³d² and the coordination number of Co₃⁺ is 6. In accordance with the VSEPR theory, a molecule with 6 bond pairs must be octahedral. 

Ans. (A) 3

Explanation: BenAl₂Si₆O₁₈

The oxidation states of each element:

Be = +2
Al = +3
Si = +4
O = -2
(2n) + (3 × 2) + (4 + 6) + (−2 × 18) = 0
Or, 

2n + 30 − 36 = 0
or 2n = 6
or n = 3

Ans. (B) A₂B₃

Explanation: A has 3 electrons in its outermost orbit and B has 6 electrons in its outermost orbit. So, element A can give three electrons to complete its octet, and element B needs 2 electrons to complete its octet. Thus, 2 atoms of element A will release 6 electrons and 3 atoms of element B will need six electrons to complete their octet. So, the formula will be A₂B₃

Ans. (C) valence electron

Explanation: In the formation of a molecule, only the outer shell electrons take part in chemical combination and they are known as valence electrons. These electrons in the outermost shell are those that become highly involved in chemical bonding. 

Ans. (B) 1

Explanation: In the antibonding orbitals, most of the electrons are located away from the space between the nuclei, resulting in a nodal plane between the nuclei. The number of nodal planes present in σ∗s anti-bonding orbitals is given as 1. The σ∗ orbital has a nodal plane that is between the nuclei and perpendicular to the internuclear axis. Therefore, option (A) is correct. 

Ans. (A) C – F

Explanation: The polar bond characteristic is proportional to the electronegativity difference between the atoms. Fluorine has a high electronegativity as compared to other atoms. So due to this difference in electronegativity, the C – F bond is the most polar bond. 

Ans. (B) Square planar, sp3d

Explanation: XeF₄ is AB₄L₂ in which the Xenon is bonded with four fluorine atoms with 4 sigma bonds and xenon has two lone pairs (4 sigma bonds and 2 lone pairs).

So, the hybridisation is sp³d². Therefore, the geometry is octahedral and the shape is square planar.

Ans. (B) 3

Explanation: In an octahedral molecule, six hybrid orbitals are directed toward the corners of a regular octahedron with a bond angle of 90°. In accordance with this geometry, the number of X - M - X bonds at 180° must be three.

Read More: Difference Between Orbit and Orbitals

Ans. (D) AlCl₃

Explanation: We know that, the extent of polarization ∝ of covalent character in ionic bonds. According to the Fajans rule, the polarising power of cation increases, with an increase in the magnitude of positive charge on the cation. Therefore, polarising the power ∝ charge of the cation.

The polarising power of an atom sees an increase with the decrease in the size of a cation, therefore, polarising (power) ∝ (1)/ (size of cation). In this particular situation, AlCl₃ satisfies the above two conditions i.e., Al is in a +3 oxidation state and also has a small size. So it has a more covalent character.

Ans. (B) acetonitrile and acetone

Explanation: Dipole-dipole interactions occur among the polar molecules. Polar molecules have permanent dipoles. Therefore, the positive pole of one molecule is attracted by the negative pole of the other molecule. In different polar molecules, the magnitude of dipole-dipole forces is estimated on the basis of the polarity of the molecules, which in turn, is dependent upon the electro negativities of the atoms present in the molecule and the geometry of the molecule.

Ans. (A) 3π and 12σ

Explanation: In Benzene (C₆H₆) ring contain 3 alternative double bond = 3π bonds and (six C-C sigma bond + six C-H sigma bond) = 12 σ bonds. A sigma bond is a covalent bond that is formed by the head on the overlap of two atomic orbitals.