Molecular Polarity Examples in Chemistry

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Molecular Polarity.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Chemistry.

Concept Recap

The overall asymmetric distribution of electric charge in a molecule, arising from the combination of individual bond polarities and the three-dimensional molecular geometry.

Even if individual bonds are polar, the molecule can be nonpolar if the dipoles cancel out symmetrically.

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How to Use These Examples

Read the first worked example with the solution open so the structure is clear.
Try the practice problems before revealing each solution.
Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Molecular Polarity starts by identifying valence electrons, likely charges or sharing, and the structure that follows.

Common stuck point: Students often know a formula related to molecular polarity but skip the recognition step: Am I explaining a substance by electron behavior, bond type, molecular shape, polarity, or attractions between particles? That leads to a correct-looking substitution attached to the wrong chemical model.

Sense of Study hint: Ask: Am I explaining a substance by electron behavior, bond type, molecular shape, polarity, or attractions between particles?

Worked Examples

Example 1

medium

Compute the dipole moment of a bond with partial charges of

\pm 0.20 e

separated by 1.20 Å. Give answer in Debye.

Answer

\approx 1.15\ \text{D}

First step

q = 0.20 \times 1.6\times 10^{-19} = 3.2\times 10^{-20}

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Example 2

hard

Water's dipole moment is 1.85 D. The O-H bond dipole is about 1.51 D and the H-O-H bond angle is 104.5°. Show the geometric calculation.

Example 3

challenge

A trigonal pyramidal

AH_3

molecule has each A-H bond dipole of 1.30 D and an H-A-H angle of 107°. Estimate the molecular dipole moment.

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

easy

Is a water molecule

H_2O

polar or nonpolar?

Example 2

easy

Is carbon dioxide

CO_2

polar or nonpolar?

Example 3

easy

What does a molecular dipole moment of zero indicate about a molecule's polarity?

Example 4

easy

Will a polar molecule dissolve well in water?

Example 5

easy

Is methane

CH_4

(tetrahedral, symmetric) polar or nonpolar?

Example 6

easy

Does a nonpolar molecule have a permanent dipole moment?

Example 7

easy

Is ammonia

NH_3

(trigonal pyramidal) polar or nonpolar?

Example 8

easy

What two factors together determine whether a molecule is polar?

Example 9

medium

BF_3

is trigonal planar with three polar B-F bonds. Is it polar or nonpolar?

Example 10

medium

Compare

CO_2

(linear) and

SO_2

(bent): which is polar?

Example 11

medium

The dipole moment is

\mu = q \times d

. If

q = 1.6 \times 10^{-19}

C and

d = 1.0 \times 10^{-10}

m, find

\mu

Example 12

medium

CCl_4

polar or nonpolar, given it is tetrahedral with four identical C-Cl bonds?

Example 13

medium

Why is water polar but

CO_2

nonpolar even though both have two polar bonds to a central atom?

Example 14

medium

A molecule has polar bonds but a measured dipole moment of zero. What does this tell you about its geometry?

Example 15

medium

Predict the polarity of

CH_3Cl

(one C-Cl bond, three C-H bonds, tetrahedral).

Example 16

medium

Which dissolves better in nonpolar hexane:

I_2

(nonpolar) or NaCl (ionic)?

Example 17

medium

NF_3

(trigonal pyramidal, polar N-F bonds) polar or nonpolar?

Example 18

challenge

CO_2

and

H_2O

both contain two polar bonds. Using vector addition of bond dipoles, explain why only water has a net dipole.

Example 19

challenge

A trigonal pyramidal molecule

AX_3

has bond dipoles that do not cancel, but the analogous trigonal planar

AX_3

does. Explain the difference.

Example 20

challenge

Rank

CCl_4

CHCl_3

, and

CH_2Cl_2

by increasing polarity and justify.

Example 21

easy

Is hydrogen sulfide

H_2S

(bent) polar or nonpolar?

Example 22

easy

SF_6

(octahedral, six identical S-F bonds) polar or nonpolar?

Example 23

easy

Does HCl have a permanent dipole moment?

Example 24

easy

XeF_4

(square planar) polar or nonpolar?

Example 25

easy

Which dissolves better in water: ethanol or hexane?

Example 26

easy

Which molecule has the larger dipole moment:

H_2O

(1.85 D) or

H_2S

(0.97 D)?

Example 27

medium

PCl_5

has five P-Cl polar bonds. The molecule is trigonal bipyramidal. Polar or nonpolar?

Example 28

medium

SF_4

has 'seesaw' geometry (one lone pair). Polar or nonpolar?

Example 29

medium

Compare

cis

- and

trans

-1,2-dichloroethylene: which is polar?

Example 30

medium

Is methanol

CH_3OH

polar?

Example 31

medium

BCl_3

(trigonal planar) and

NCl_3

(trigonal pyramidal) both contain only polar B-Cl or N-Cl bonds. Which is nonpolar?

Example 32

medium

Predict whether

CS_2

(linear like

CO_2

) is polar or nonpolar.

Example 33

medium

Is acetone

(CH_3)_2C=O

polar?

Example 34

medium

Rank the molecules

CH_4

CH_3Cl

CH_2Cl_2

by increasing dipole moment.

Example 35

medium

Which polar molecule has hydrogen bonding:

NH_3

PH_3

Example 36

hard

XeF_2

is linear with three lone pairs on Xe. Polar or nonpolar?

Example 37

hard

Why does

NH_3

(1.47 D) have a smaller dipole moment than

H_2O

(1.85 D) even though it has three polar N-H bonds vs water's two?

Example 38

hard

If a tetrahedral molecule

AX_4

has two X atoms replaced by Y (so

AX_2Y_2

, e.g.,

CH_2Cl_2

), is it always polar?

Example 39

hard

Predict whether ozone

O_3

(bent) has a dipole moment despite all atoms being oxygen.

Example 40

hard

Boiling points:

CH_4

(−161 °C),

NH_3

(−33 °C),

H_2O

(100 °C),

HF

(20 °C). Explain the role of molecular polarity.

Example 41

hard

Which solvent dissolves

I_2

better: water or

CCl_4

? Justify with polarity.

Example 42

hard

BF_3

(planar, 0 D) reacts with

NH_3

(pyramidal, 1.47 D) to form

H_3N-BF_3

. Why is the adduct polar?

Example 43

challenge

Why is

cis

-2-butene only weakly polar (~0.3 D) even though it lacks the symmetry of

trans

-2-butene?

Example 44

challenge

Predict the polarity ordering of

para

meta

-, and

ortho

-dichlorobenzene.

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Related Concepts

Polar Covalent Bond Molecular Geometry Intermolecular Forces Hydrogen Bonding

Background Knowledge

These ideas may be useful before you work through the harder examples.

polar covalentmolecular geometry