Chemical Bonding & Molecular Structure Quiz - ICSE Class 11 Chemistry
Free practice quiz: Chemical Bonding & Molecular Structure (ICSE Class 11 Chemistry). 49 multiple-choice questions with answers and explanations. Play online, no sign-up needed.
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Which of the following molecules exhibits both sigma and pi bonds in its bonding structure?
- H₂
- O₂
- N₂
- C₂H₂
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Answer: D. C₂H₂
Acetylene (C₂H₂) has a triple bond between the carbon atoms (one sigma, two pi) and single bonds between each carbon and hydrogen (sigma bonds). Hydrogen (H₂) has a single sigma bond. Oxygen (O₂) has a double bond (one sigma, one pi). Nitrogen (N₂) has a triple bond (one sigma, two pi). The question asks for a molecule exhibiting *both* sigma and pi bonds within its structure, and C₂H₂ fits this perfectly with its C-C triple bond.
According to Fajan's rules, covalent character in an ionic bond increases with:
- Larger cation size, smaller anion charge
- Smaller cation size, larger anion charge
- Larger cation size, larger anion charge
- Smaller cation size, smaller anion charge
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Answer: B. Smaller cation size, larger anion charge
Fajan's rules state that covalent character increases with: 1. Small cation size (high charge density), 2. Large anion size (easily polarizable), 3. High charge on cation and anion. Therefore, a smaller cation and a larger anion, both with higher charges, will lead to greater polarization and thus more covalent character.
Which of the following is NOT a characteristic of a polar covalent bond?
- Unequal sharing of electrons
- Presence of a dipole moment
- Formation due to large electronegativity difference
- Complete transfer of electrons
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Answer: D. Complete transfer of electrons
A polar covalent bond is characterized by unequal sharing of electrons due to a significant electronegativity difference between the bonded atoms, resulting in a partial positive charge on one atom and a partial negative charge on the other, creating a dipole moment. Complete transfer of electrons leads to the formation of ionic bonds.
The hybridization of the central sulfur atom in SO₂ is:
- sp
- sp²
- sp³
- dsp²
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Answer: B. sp²
In SO₂, sulfur is bonded to two oxygen atoms and has one lone pair. The Lewis structure shows a double bond between S and one O, and a single bond with a coordinate bond to the other O, or resonance structures with partial double bonds. In VSEPR terms, sulfur has 3 electron groups (2 bonding domains + 1 lone pair). This corresponds to sp² hybridization, leading to a bent molecular geometry.
The presence of a lone pair of electrons on the central atom of a molecule will generally cause:
- An increase in bond angle
- A decrease in bond angle
- No change in bond angle
- Rotation around bonds
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Answer: B. A decrease in bond angle
Lone pairs of electrons occupy more space and exert greater repulsive forces on bonding pairs than bonding pairs do on each other. This repulsion pushes the bonding pairs closer together, leading to a decrease in bond angles compared to a molecule with the same hybridization but no lone pairs.