Question 1

Which of the following statements best explains why CO$$_2 is a $$nonpolar molecule, even though it contains polar bonds?

Accepted Answer

The molecule is linear, so the bond dipoles cancel each other out, resulting in a net dipole moment of $$\mu = 0.$$

Question 2

According to valence bond theory, what is required for a covalent bond to form between two atoms?

Accepted Answer

Overlap of two half-filled atomic orbitals, each containing one electron of opposite spin.

Question 3

Which of the following molecules is expected to have the highest boiling point, and why?

Accepted Answer

A polar isomer of dichloroethylene, because its nonzero dipole moment leads to stronger intermolecular forces.

Question 4

Which criterion is NOT used to determine the relative importance of resonance structures?

Accepted Answer

The total number of atoms in the molecule.

Question 5

What is the molecular geometry and approximate bond angle of CH$$_4$$ according to the VSEPR model and hybridization theory?

Accepted Answer

Tetrahedral geometry with bond angles of $$109.5^\circ$$ due to $$sp^3$$ hybridization.

Question 6

Which of the following best describes the effect of molecular polarity on physical properties?

Accepted Answer

Molecular polarity increases boiling and melting points due to stronger intermolecular forces.

Question 7

Which statement about the bonding in H$$_2O is $$correct according to valence bond theory and hybridization?

Accepted Answer

The oxygen atom uses $$sp^3$$ hybrid orbitals to form two sigma bonds with hydrogen atoms, resulting in a bent molecular shape.

Question 8

Which of the following molecules is nonpolar due to its molecular geometry, despite having polar bonds?

Accepted Answer

CO$$_2$$

Question 9

What is the main reason that the four bonds in CH$$_4$$ are equivalent and have the same bond angle?

Accepted Answer

The central carbon atom undergoes $$sp^3$$ hybridization, forming four equivalent hybrid orbitals.

Question 10

Which of the following best describes the bonding in HCl according to valence bond theory?

Accepted Answer

A half-filled 1s orbital of hydrogen overlaps with a half-filled 3p orbital of chlorine, forming a sigma bond.

Question 11

Which of the following is a correct statement about resonance hybrids?

Accepted Answer

The actual electronic structure is a weighted average of all valid resonance structures.

Question 12

Which molecule would you expect to be polar based on both bond polarity and molecular shape?

Accepted Answer

H$$_2O$$, because it has polar bonds and a bent shape.

Question 13

Which of the following is true about the directionality of covalent bonds?

Accepted Answer

Bonds formed by orbitals other than s orbitals have directionality due to the shape of the overlapping orbitals.

Question 14

Which hybridization is associated with a central atom that has four charge clouds?

Accepted Answer

$$sp^3$$ hybridization

Question 15

A molecule has a trigonal pyramidal shape and bond angles close to $$109.5^\circ. $$Which molecule fits this description and what is its hybridization?

Accepted Answer

NH$$_3$$ with $$sp^3$$ hybridization

Question 16

Which of the following best explains why the bond angles in H$$_2O $$are less than $$109.5^\circ$$?

Accepted Answer

The presence of two lone pairs on oxygen causes greater repulsion, reducing the bond angle from the ideal $$sp^3$$ value.

Question 17

Which of the following statements about the VSEPR model is correct?

Accepted Answer

The VSEPR model predicts that charge clouds around a central atom arrange themselves to minimize electron-electron repulsions.

Question 18

Which of the following is true about the overlap of atomic orbitals in covalent bonding?

Accepted Answer

The greater the orbital overlap, the stronger the covalent bond.

Question 19

Which molecule would you expect to be nonpolar, even though it contains polar bonds, due to its geometry?

Accepted Answer

SF$$_6$$

Molecular Polarity, Valence Bond Theory, and Hybridization: Study Notes

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