Question 1

In a covalent bond, electrons are shared between atoms. Which of the following best describes the nature of a coordinate covalent bond (dative bond)?

Accepted Answer

A coordinate covalent bond forms when both electrons in the shared pair come from a single donor atom, which donates to an acceptor atom that provides the orbital.

Question 2

The bond angle in a water molecule (H₂O) is approximately 104.5° instead of 120°. This deviation from the expected tetrahedral angle is primarily due to:

Accepted Answer

According to VSEPR theory, the two lone pairs on oxygen repel the bonding pairs more strongly than bonding pairs repel each other, reducing the bond angle from 109.5° to 104.5°.

Question 3

Which of the following molecules exhibits sp hybridization in its central atom?

Accepted Answer

In CO₂, the carbon atom forms two double bonds with oxygen atoms using sp hybridization, resulting in a linear molecular geometry with 180° bond angles.

Question 4

The electronegativity values of C, N, and O are approximately 2.5, 3.0, and 3.5 respectively. Which bond is most polar?

Accepted Answer

The C—O bond has the largest electronegativity difference (3.5 − 2.5 = 1.0), making it the most polar among the three bonds.

Question 5

In the ammonia molecule (NH₃), the molecular geometry is trigonal pyramidal while the electron geometry is tetrahedral. What accounts for this difference?

Accepted Answer

Electron geometry considers all electron pairs (bonding and lone pairs) giving tetrahedral, while molecular geometry considers only bonding pairs, giving trigonal pyramidal due to the one lone pair on nitrogen.

Question 6

Which of the following molecules exhibits sp hybridization in its central atom?

Accepted Answer

CO₂ has a linear structure with the central carbon atom bonded to two oxygen atoms via double bonds, resulting in sp hybridization.

Question 7

The bond angle in NH₃ is approximately 107°, while in CH₄ it is 109.5°. This difference is primarily due to:

Accepted Answer

NH₃ has one lone pair on nitrogen which exerts greater repulsion than bonding pairs, compressing the bond angle from the tetrahedral 109.5° to 107°.

Question 8

In the Lewis structure of PCl₅, the number of bonding pairs and lone pairs on the central phosphorus atom are respectively:

Accepted Answer

PCl₅ has five P-Cl bonds and no lone pairs on phosphorus, giving a trigonal bipyramidal molecular geometry.

Question 9

Which of the following molecules is polar despite having a symmetrical molecular geometry?

Accepted Answer

H₂O has a bent (asymmetrical) geometry due to two lone pairs on oxygen, making it polar; the others listed are nonpolar due to symmetrical arrangements.

Question 10

The molecular geometry of SF₆ is octahedral because the central sulfur atom is bonded to six fluorine atoms with:

Accepted Answer

SF₆ requires six hybrid orbitals for six bonds, achieved through sp³d² hybridization of sulfur.

Question 11

In the molecule N₂, the bond order is 3. This indicates the presence of:

Accepted Answer

N₂ has a triple bond consisting of one σ bond and two π bonds, giving a bond order of 3 and exceptional stability.

Question 12

The VSEPR theory predicts that ClF₃ has a molecular geometry of:

Accepted Answer

ClF₃ has five electron pairs (three bonding, two lone pairs) around chlorine, resulting in a T-shaped molecular geometry from octahedral electron geometry.

Question 13

Which of the following compounds exhibits resonance structures?

Accepted Answer

NO₃⁻ has multiple valid Lewis structures with different positions of the double bond, characteristic of resonance stabilization.

Question 14

A molecule has a bond order of 2.5 between two atoms. Which of the following statements is CORRECT regarding this bond?

Accepted Answer

A bond order of 2.5 indicates the bond length falls between a double bond (order 2) and triple bond (order 3), with stronger bonds being shorter; bond order inversely correlates with bond length.

Question 15

In the molecular orbital diagram of O₂, the two unpaired electrons occupy which orbitals?

Accepted Answer

O₂ has configuration (π2p)⁴(π2p*)², placing both unpaired electrons in the degenerate π2p* antibonding orbitals, making it paramagnetic.

Question 16

The H–O–H bond angle in water is approximately 104.5° instead of the expected 109.5° from sp³ hybridization. Which factor is primarily responsible for this deviation?

Accepted Answer

The two lone pairs on oxygen repel bonding pairs more strongly than bonding pairs repel each other, compressing the H–O–H angle from the tetrahedral 109.5° to 104.5°.

AFCAT Chemical Bonding & Molecular Structure

Chemical Bonding & Molecular Structure — Practice Questions