A1 - Intermolecular Forces

Question 1

Which substances have intermolecular forces between molecules?

Answer 1

Simple molecules

Question 2

Are intermolecular forces strong or weak?

Answer 2

Weak

Question 3

What are the three types of intermolecular forces?

Answer 3

Hydrogen bonding, Permanent dipole-dipole, Induced dipole-dipole

Question 4

Which is the strongest type of intermolecular force?

Answer 4

Hydrogen bonding

Question 5

Which is the weakest type of intermolecular force?

Answer 5

Induced dipole-dipole

Question 6

What is a non-polar molecule?

Answer 6

A non-polar molecule has electrons distributed evenly throughout the molecule.

Question 7

What is a polar molecule?

Answer 7

A polar molecule has an uneven electron distribution, with a partial positive charge on one part of the molecule and a partial negative on another part.

Question 8

When substances with a simple molecular structure are melted or boiled what is broken?

Answer 8

Weak intermolecular forces are broken

Question 9

Do simple molecules have a high melting point or a low melting point?

Answer 9

Low. The weak intermolecular forces between molecules are broken.

Question 10

What is the strongest intermolecular force between polar molecules?

Answer 10

Permanent dipole-dipole

Question 11

What is the strongest intermolecular force between non-polar molecules?

Answer 11

Induced dipole-dipole

Question 12

What is the strongest type of intermolecular force between simple molecules that have a H bonded to an N, O or F?

Answer 12

Hydrogen bonding

Question 13

How do you know if simple molecules have hydrogen bonding between them?

Answer 13

• They have a H bonded to an N, O or F.
• A lone pair of electrons on the fluorine, oxygen or nitrogen

Question 14

Hydrogen bonding is the strongest type of intermolecular force, true or false?

Answer 14

True

Question 15

Induced dipole-dipole is the weakest type of intermolecular force, true or false?

Answer 15

True

Question 16

Explain how is an induced dipole-dipole intermolecular force is formed between 2 non-polar molecules.

Answer 16

• Fluctuation in electron density
• Creates a temporary dipole in one molecule
• This induces a dipole in a neighbouring molecule

Question 17

If the strongest intermolecular force between molecules is Hydrogen bonding, which other intermolecular forces do they also have?

Answer 17

Permanent dipole-dipole and Induced dipole-dipole

Question 18

If the strongest intermolecular force between molecule is permanent dipole-dipole, which other intermolecular force do they also have?

Answer 18

Induced dipole-dipole

Question 19

Non-polar molecules only have induced dipole-dipole forces between molecules, true or false?

Answer 19

True

Question 20

What increases the strength of induced dipole-dipole forces?

Answer 20

More electrons
More surface contact area

Question 21

Which has stronger induced dipole-dipole, Cl2 or Br2 ?

Answer 21

Br2. It has more electrons

Question 22

Which has stronger induced dipole-dipole, F2 or I2 ?

Answer 22

I2. It has more electrons

Question 23

Which has stronger induced dipole-dipole, S8 or P4 ?

Answer 23

P4. Bigger molecules so has more electrons

Question 24

Which has stronger induced dipole-dipole, C3H8 or C4H10?

Answer 24

C4H10. Bigger molecules so has more electrons

Question 25

Which has a higher boiling point, Cl2 or Br2 ?

Answer 25

Br2. It has more electrons so stronger induced dipole-dipole.

Question 26

Which has a higher boiling point, F2 or I2 ?

Answer 26

I2. It has more electrons so stronger induced dipole-dipole.

Question 27

Is CCl4 polar or non-polar molecule? (Clue: Draw it out with partial charges. Do they cancel out?)

Answer 27

Non-polar
Partial charges cancel out

Question 28

Is CHCl3 polar or non-polar molecule? (Clue: Draw it out with partial charges.

Answer 28

Do they cancel out?)
Polar
Partial charges do not cancel out

Question 29

Why does HBr have a higher boiling point than HCl? (Clue: is it polar or non-polar? What are all the types of intermolecular force it will have?)

Answer 29

Both polar molecules
Strongest intermolecular force is permanent dipole-dipole.
It will also have induced dipole-dipole.
HBr has more electrons that HCl, stronger induced dipole-dipole attraction.

Question 30

Why does HI have a higher boiling point than HCl? (Clue: is it polar or non-polar? What other intermolecular force will it also have?)

Answer 30

Both polar molecules
Strongest intermolecular force is Permanent dipole-dipole.
It will also have induced dipole-dipole.
HI has more electrons that HCl, stronger induced dipole-dipole attraction.

Question 31

Why does HI have a higher boiling point than HF? (Clue: is it polar or non-polar? What other intermolecular force will it also have?)

Answer 31

Both polar molecules
Strongest intermolecular force is Permanent dipole-dipole.
It will also have induced dipole-dipole.
HI has more electrons that HF, stronger induced dipole-dipole attraction.