Here below some basic mCQ’s about “Valence Bond Theory” with answer which is explained in details. Let’s check one by one.
- Which of the following bonds is best explained by Valence Bond Theory?
A. Ionic bond
B. Covalent bond
C. Metallic bond
D. Hydrogen bond
Answer: B. Covalent bond
Explanation: VBT is used to explain the formation of covalent bonds through the overlap of atomic orbitals. It doesn’t apply to ionic, metallic, or hydrogen bonds.
- According to VBT, a sigma (σ) bond forms by:
A. Side-to-side overlap of p-orbitals
B. End-to-end overlap of orbitals
C. Overlap of d-orbitals
D. Overlap of f-orbitals
Answer: B. End-to-end overlap of orbitals
Explanation: A sigma bond forms when atomic orbitals overlap directly along the internuclear axis, which is end-to-end overlap, providing maximum overlap.
- In a double bond between two atoms, the bond consists of:
A. One sigma bond and two pi bonds
B. Two sigma bonds
C. One sigma bond and one pi bond
D. Two pi bonds
Answer: C. One sigma bond and one pi bond
Explanation: In a double bond, one bond is a sigma bond (from head-on overlap) and the other is a pi bond (from side-to-side overlap of p-orbitals).
- Which of the following molecules is sp³ hybridized according to VBT?
A. CH₄
B. CO₂
C. BF₃
D. BeCl₂
Answer: A. CH₄
Explanation: In methane (CH₄), carbon undergoes sp³ hybridization, where one s and three p orbitals mix to form four equivalent sp³ hybrid orbitals, creating a tetrahedral shape.
- Valence Bond Theory explains that in an NH₃ molecule, the nitrogen atom forms:
A. Three sigma bonds and one lone pair
B. Four sigma bonds
C. Two sigma bonds and two lone pairs
D. Three pi bonds and one lone pair
Answer: A. Three sigma bonds and one lone pair
Explanation: In ammonia (NH₃), nitrogen forms three sigma bonds with hydrogen atoms and retains one lone pair of electrons.
- Which type of orbital overlap leads to the formation of a pi bond?
A. Overlap along the internuclear axis
B. Lateral overlap of p-orbitals
C. Head-on overlap of s-orbitals
D. Overlap of d-orbitals
Answer: B. Lateral overlap of p-orbitals
Explanation: A pi bond forms when two p-orbitals overlap sideways, leading to a bond above and below the plane of the atoms involved.
- According to VBT, the bond angle in water (H₂O) is approximately:
A. 109.5°
B. 104.5°
C. 120°
D. 180°
Answer: B. 104.5°
Explanation: Water (H₂O) has a bent shape due to sp³ hybridization of oxygen. Two lone pairs reduce the bond angle to approximately 104.5° instead of the ideal tetrahedral angle of 109.5°.
- According to VBT, in the formation of H₂ molecule:
A. The two hydrogen atoms do not overlap
B. There is no overlap of orbitals
C. The 1s orbitals of two hydrogen atoms overlap
D. The 2p orbitals of two hydrogen atoms overlap
Answer: C. The 1s orbitals of two hydrogen atoms overlap
Explanation: The H₂ molecule forms when the 1s orbitals of two hydrogen atoms overlap, resulting in the formation of a sigma bond.
- In Valence Bond Theory, hybridization helps to:
A. Minimize the bond angles
B. Explain the magnetic properties of molecules
C. Explain the shape and geometry of molecules
D. Create molecular orbitals
Answer: C. Explain the shape and geometry of molecules
Explanation: Hybridization explains the shape and geometry of molecules by mixing atomic orbitals to form hybrid orbitals, which determine the bond angles.
- In VBT, why is the bond angle in NH₃ smaller than the bond angle in CH₄?
A. Because nitrogen has lone pairs
B. Because hydrogen atoms are smaller in NH₃
C. Because nitrogen is more electronegative
D. Because ammonia has more pi bonds
Answer: A. Because nitrogen has lone pairs
Explanation: The lone pair-bond pair repulsion in NH₃ forces the bond angles to decrease from the ideal tetrahedral angle of 109.5° (in CH₄) to around 107°.
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