Question 1

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

Accepted Answer

The molecule is nonpolar because the bond dipoles are equal in magnitude and point in exactly opposite directions, resulting in a net dipole moment of zero.

Question 2

What is the molecular geometry and approximate bond angle of NH$$_3$$ according to the VSEPR model?

Accepted Answer

Trigonal pyramidal, $$\approx 107.3^\circ$$

Question 3

Which hybridization corresponds to a central atom with four electron domains (bonding and lone pairs) around it?

Accepted Answer

$$sp^3$$

Question 4

In the molecule BeCl$$_2$$, what is the hybridization of the beryllium atom and what is the molecular geometry?

Accepted Answer

Hybridization: $$sp$$, Geometry: linear

Question 5

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

Accepted Answer

Electron-pair geometry: tetrahedral; Molecular geometry: trigonal pyramidal

Question 6

Which of the following molecules is expected to be polar based on its molecular geometry and the presence of lone pairs?

Accepted Answer

H$$_2O$$

Question 7

What is the hybridization of the central atom in SF$$_6$$ and what is its molecular geometry?

Accepted Answer

Hybridization: $$sp^3d^2$, Geometry: octahedral

Question 8

Which of the following best describes the difference between a sigma ($$\sigma) $$bond and a pi ($$\pi) $$bond?

Accepted Answer

A $$\sigma$$ bond is formed by head-to-head overlap of orbitals along the internuclear axis, while a $$\pi$$ bond is formed by sideways overlap of p orbitals above and below the plane of the nuclei.

Question 9

How many sigma ($$\sigma) $$and pi ($$\pi) $$bonds are present in the acetic acid (CH$$_3$$COOH) molecule?

Accepted Answer

$$7\ \sigma$$ bonds, $$1\ \pi$$ bond

Question 10

Which of the following molecules has a central atom with $$sp^2$$ hybridization?

Accepted Answer

BF$$_3$$

Question 11

A molecule has two bonding pairs and two lone pairs on the central atom. What is its molecular geometry and approximate bond angle?

Accepted Answer

Bent, $$\u003c109.5^\circ$$

Question 12

What is the dipole moment ($$\mu) of a $$molecule defined as?

Accepted Answer

$$\mu = Q 	imes r$$

Question 13

Which of the following is true about the bond angles in H$$_2O $$compared to NH$$_3$$ and CH$$_4$$?

Accepted Answer

The bond angle in H$$_2O$$ ($$104.5^\circ) is $$less than that in NH$$_3$$ ($$107.3^\circ) $$and CH$$_4$$ ($$109.5^\circ) $$due to increased lone pair repulsion.

Question 14

Which of the following molecules has a central atom with $$sp^3d$ hybridization?

Accepted Answer

PCl$$_5$$

Question 15

In the molecule H$$_2$$CCN, how many sigma ($$\sigma) $$and pi ($$\pi) $$bonds are present?

Accepted Answer

5 $$\sigma$$ bonds, 2 $$\pi$$ bonds

Question 16

Which of the following best describes the hybridization of the carbon atoms in ethylene (C$$_2H$_4$$)?

Accepted Answer

Each carbon atom is $$sp^2$$ hybridized.

Question 17

Which of the following is a correct statement about lone pairs and molecular polarity?

Accepted Answer

Molecules with lone pairs on the central atom are generally polar.

Question 18

What is the electron-pair geometry and hybridization of the central atom in NO$$_3^-$$?

Accepted Answer

Trigonal planar, $$sp^2$$

Question 19

Which of the following is true about the formation of covalent bonds according to valence bond theory?

Accepted Answer

Covalent bonds are formed from the overlap of valence orbitals on each atom involved in the bond.

Chemical Bonding II: Molecular Geometry and Hybridization of Atomic Orbitals

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