Question 1

Which of the following statements best explains why water ($$\mathrm{H_2O}) is a $$polar molecule?

Accepted Answer

Water has polar bonds and an asymmetrical (bent) shape, resulting in a net dipole moment.

Question 2

Given the electronegativities: H = 2.1, O = 3.5, S = 2.5, P = 2.1, F = 4.0, which bond is the most polar?

Accepted Answer

P-F

Question 3

A molecule of carbon dioxide ($$\mathrm{CO_2$}) is $$composed of two polar bonds. Why is $$\mathrm{CO_2$}$$ considered nonpolar?

Accepted Answer

The molecule is linear and symmetrical, so the dipoles cancel each other out.

Question 4

Which of the following intermolecular forces is the strongest?

Accepted Answer

Ionic bonds

Question 5

What is the difference in electronegativity ($$\Delta EN) $$for the S-O bond, given S = 2.5 and O = 3.5?

Accepted Answer

$$\Delta EN = 1.0$$

Question 6

Which of the following molecules can form hydrogen bonds with water?

Accepted Answer

Ethanol ($$\mathrm{CH_3CH_2OH})$$

Question 7

A soap molecule has a long hydrocarbon tail and a polar head. Which part is hydrophobic?

Accepted Answer

The hydrocarbon tail

Question 8

Which type of bond involves the equal sharing of valence electrons between two atoms?

Accepted Answer

Nonpolar covalent bond

Question 9

Why do oil and water not mix well?

Accepted Answer

Oil is nonpolar and water is polar, so there is little attraction between their molecules.

Question 10

Which of the following best describes London dispersion forces?

Accepted Answer

Temporary attractions caused by momentary uneven distribution of electrons.

Question 11

A molecule has polar bonds but is symmetrical in shape. What is the overall polarity of the molecule?

Accepted Answer

The molecule is nonpolar because the dipoles cancel out.

Question 12

Which of the following molecules will have the strongest dipole-dipole interactions?

Accepted Answer

Ammonia ($$\mathrm{NH_3$})$$

Question 13

Which of the following is true about hydrogen bonds?

Accepted Answer

They occur between molecules containing O-H, N-H, or F-H bonds.

Question 14

If a molecule has a region with only C-H bonds, what can you infer about that region?

Accepted Answer

It is hydrophobic and will not form strong attractions with water.

Question 15

Which of the following best describes a dipole-dipole interaction?

Accepted Answer

An attraction between partial charges in polar molecules.

Question 16

Rank the following intermolecular forces from weakest to strongest: London dispersion, dipole-dipole, hydrogen bond.

Accepted Answer

London dispersion \u003c dipole-dipole \u003c hydrogen bond

Question 17

Which of the following pairs of atoms will form an ionic bond?

Accepted Answer

Ca and Br

Question 18

What is the main reason that molecules with O-H, N-H, or F-H bonds have unusually high boiling points?

Accepted Answer

They have strong hydrogen bonds between molecules.

Question 19

Which of the following best describes a hydrophilic molecule?

Accepted Answer

A molecule that is polar and attracts water.

Question 20

A molecule has a large surface area and is nonpolar. What type of intermolecular force will be most significant for this molecule?

Accepted Answer

London dispersion forces

Molecular Polarity and Intermolecular Forces

Study Guide - Practice Questions