1.5.3 Types of Forces Between Molecules (Physical Chemistry)

Question 1

Intramolecular forces are

Answer 1

forces within a molecule and are usually covalent bonds

Question 2

Covalent bonds are

Answer 2

formed when the outer electrons of two atoms are shared

Question 3

Single, double, triple and co-ordinate bonds are all types of

Answer 3

intramolecular forces

Question 4

Intramolecular Forces vs. Intermolecular Forces diagram

Answer 4

Question 5

Molecules also contain weaker

Answer 5

intermolecular forces

Question 6

Molecules also contain weaker intermolecular forces which are

Answer 6

forces between the molecules

Question 7

There are three types of intermolecular forces:

Answer 7

• induced dipole – dipole forces
• permanent dipole – dipole forces
• hydrogen bonding

Question 8

Induced dipole – dipole forces

Answer 8

also called van der Waals or London dispersion forces

Question 9

Permanent dipole – dipole forces are

Answer 9

the attractive forces between two neighbouring molecules with a permanent dipole

Question 10

Hydrogen Bonding are

Answer 10

a special type of permanent dipole - permanent dipole forces

Question 11

Intramolecular forces are stronger than

Answer 11

intermolecular forces

Question 12

The strengths of the types of bond or force are as follows:

Answer 12

Question 13

When two atoms in a covalent bond have the same electronegativity the covalent bond is

Answer 13

nonpolar

Question 14

The two chlorine atoms have the same electronegativities so the bonding electrons are shared equally between the two atoms diagram

Answer 14

Question 15

When two atoms in a covalent bond have different electronegativities the covalent bond is

Answer 15

polar

Question 16

When two atoms in a covalent bond have different electronegativities the covalent bond is polar and the electrons will be drawn towards

Answer 16

the more electronegative atom

Question 17

As a result of this:
The negative charge centre and positive charge centre do not

Answer 17

coincide with each other

Question 18

As a result of this:
This means that the electron distribution is

Answer 18

asymmetric

Question 19

As a result of this:
The less electronegative atom gets a partial charge of

Answer 19

δ+ (delta positive)

Question 20

As a result of this:
The more electronegative atom gets a partial charge of

Answer 20

δ- (delta negative)

Question 21

The greater the difference in electronegativity the more

Answer 21

polar the bond becomes

Question 22

Cl has a greater electronegativity than H causing the electrons to be more attracted towards the Cl atom which becomes delta negative and the H delta positive diagram

Answer 22

Question 23

Polar molecules have what type of force

Answer 23

permanent dipoles

Question 24

Permanent dipole - dipole forces:
The molecule will always have

Answer 24

a negatively and positively charged end

Question 25

Permanent dipole - dipole forces diagram

Answer 25

Question 26

Forces between two molecules that have permanent dipoles are called

Answer 26

permanent dipole - dipole forces

Question 27

The δ+ end of the dipole in one molecule and the δ- end of the dipole in a neighbouring molecule are

Answer 27

attracted towards each other

Question 28

Induced dipole - dipole forces exist between

Answer 28

all atoms or molecules

Question 29

Induced dipole - dipole forces are also known as

Answer 29

van der Waals forces or London dispersion forces

Question 30

Induced Dipole-Dipole Forces diagram

Answer 30

Question 31

The electron charge cloud in non-polar molecules or atoms are

Answer 31

constantly moving

Question 32

During this movement, the electron charge cloud can be

Answer 32

more on one side of the atom or molecule than the other

Question 33

This causes a

Answer 33

temporary dipole to arise

Question 34

This temporary dipole can

Answer 34

induce a dipole on neighbouring molecules

Question 35

When this happens, the δ+ end of the dipole in one molecule and the δ- end of the dipole in a neighbouring molecule are

Answer 35

attracted towards each other

Question 36

Because the electron clouds are moving constantly, the dipoles are

Answer 36

only temporary

Question 37

For small molecules with the same number of electrons, permanent dipoles are stronger than

Answer 37

induced dipoles

Question 38

Propanone has a higher boiling point than butane in terms of relative strength of induced dipole-dipole forces

Answer 38

• butane and propanone have the same number of electrons
• butane is a nonpolar molecule and will have induced dipole forces
• propanone is a polar molecule and will have permanent dipole forces
• therefore, more energy is required to break the intermolecular forces between propanone molecules than between butane molecules
• so, propanone has a higher boiling point than butane

Question 39

Pd-pd forces are stronger than id-id forces in smaller molecules with an equal number of electrons diagram

Answer 39

Question 40

Hydrogen bonding is the strongest form of

Answer 40

intermolecular bonding

Question 41

Intermolecular bonds are bonds between

Answer 41

molecules

Question 42

Hydrogen bonding is a type of

Answer 42

permanent dipole – permanent dipole bonding

Question 43

For hydrogen bonding to take place the following is needed:

Answer 43

a species which has an O, N or F (very electronegative) atom bonded to a hydrogen

Question 44

When hydrogen is covalently bonded to an O, N or F, the bond becomes

Answer 44

highly polarised

Question 45

The H becomes so δ+ charged that it can

Answer 45

form a bond with the lone pair of an O, N or F atom in another molecule

Question 46

The H becomes so δ+ charged that it can form a bond with the lone pair
For example, in water

Answer 46

water can form two hydrogen bonds, because the O has two lone pairs

Question 47

Hydrogen bonding in water diagram

Answer 47