Question 1

Which of the following molecules has a trigonal planar molecular geometry, and what is the approximate bond angle between its atoms?

Accepted Answer

BF3, 120°

Question 2

According to VSEPR theory, what is the electron geometry and molecular geometry of water (H2O)?

Accepted Answer

Electron geometry: tetrahedral; Molecular geometry: bent

Question 3

Which of the following statements best explains why the bond angle in ammonia (NH3) is less than the ideal tetrahedral angle?

Accepted Answer

The lone pair on nitrogen repels the bonding pairs more strongly, reducing the bond angle.

Question 4

Which molecule below is nonpolar despite having polar bonds, and why?

Accepted Answer

CO2, because its linear geometry causes the bond dipoles to cancel.

Question 5

Given the Lewis structure for ozone (O3), which statement about its bonding is correct?

Accepted Answer

Ozone has resonance structures with delocalized electrons shared across all three oxygen atoms.

Question 6

Which of the following molecules can expand its octet and why?

Accepted Answer

SF4, because sulfur is in period 3 and can use d orbitals.

Question 7

Calculate the enthalpy change ($$\Delta H) $$for the reaction: $$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$, using the following average bond energies (in kJ/mol): $$\mathrm{C-H}$$: 414, $$\mathrm{O=O}$$: 498, $$\mathrm{C=O}$$: 799, $$\mathrm{O-H}$$: 464.

Accepted Answer

$$\Delta H = -802 kJ$$

Question 8

Which of the following best describes the difference between localized and delocalized electrons in resonance structures?

Accepted Answer

Localized electrons are confined between two atoms, while delocalized electrons are shared across more than two atoms.

Question 9

Which molecule has a T-shaped molecular geometry, and what is the electron geometry around the central atom?

Accepted Answer

BrF3; electron geometry is trigonal bipyramidal

Question 10

Which of the following bonds is the shortest, based on average bond lengths?

Accepted Answer

$$\mathrm{N \equiv N}$$

Question 11

Why does the lone pair on the central atom in a molecule like SF4 prefer the equatorial position in a trigonal bipyramidal geometry?

Accepted Answer

It minimizes the number of 90° lone pair-bonding pair repulsions.

Question 12

Which of the following molecules is expected to have a net dipole moment?

Accepted Answer

CH2F2

Question 13

Which of the following statements about bond energy is correct?

Accepted Answer

Triple bonds have higher bond energies than single bonds between the same atoms.

Question 14

Which molecule has an octahedral electron geometry but a square planar molecular geometry?

Accepted Answer

XeF4

Question 15

A molecule has four bonding pairs and one lone pair around the central atom. What is its electron geometry and molecular geometry?

Accepted Answer

Electron geometry: trigonal bipyramidal; Molecular geometry: seesaw

Question 16

Which of the following best explains why the bond angle in H2O is less than the ideal tetrahedral angle?

Accepted Answer

The two lone pairs on oxygen repel the bonding pairs more strongly, reducing the bond angle.

Question 17

Which of the following molecules is expected to be nonpolar due to its molecular geometry?

Accepted Answer

CCl4

Question 18

Which of the following is the best resonance structure for a molecule?

Accepted Answer

The one that minimizes formal charges and places negative formal charge on the most electronegative atom.

Question 19

Which of the following molecules has a square pyramidal molecular geometry?

Accepted Answer

BrF5

Question 20

Which of the following statements about bond length is correct?

Accepted Answer

Bond length decreases as bond multiplicity increases.

Covalent Bonding, Molecular Geometry, Resonance, and Bond Energies

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