Chapter 3.7 - Forces Acting Between Molecules

Question 1

Name the 3 types of intermolecular forces :

Answer 1

• Van der Waals forces
• Dipole Dipole (permanent dipole)
• Hydrogen bonding

Question 2

Explain hydrogen bonding

Answer 2

-hydrogen bonding only happens when hydrogen is covalently bonded to fluorine, nitrogen or oxygen

Question 3

Explain how hydrogen bond has a huge effect on the property of the substance:

Answer 3

Substances with hydrogen bond have high boiling point and mp

Question 4

State the strongest type of interaction that occurs between molecules of hydrogen peroxide and water

Answer 4

Hydrogen bonding

Question 5

Name the strongest attractive force between two ammonia molecules.

Answer 5

Hydrogen bonding

Question 6

State the strongest type of intermolecular force between hydrogen fluoride molecules.

Answer 6

Hydrogen bonding

Question 7

In terms of intermolecular forces, suggest the main reason why phosphine is almost insoluble in water. (1)

Answer 7

Phosphine does not form hydrogen bonds with water

Question 8

Explain, in terms of bonding, why the boiling point of fluorine is very low (1)

Answer 8

Weak van der waals forces between molecules

Question 9

Fluorine and iodine are elements in Group 7 of the Periodic Table.
Explain why iodine has a higher melting point than fluorine. (2)

Answer 9

• iodine has more electrons,

- stronger van der waals forces between molecules

Question 10

State the strongest type of intermolecular force in a sample of NHF2

Answer 10

Hydrogen bonding

Question 11

State the strongest type of intermolecular force holding the water molecules together in the ice crystal

Answer 11

Hydrogen bonding

Question 12

State the strongest type of intermolecular force in methane

Answer 12

Van der waals forces

Question 13

Give one reason why the melting point of ice is higher than the melting point of methane.(1)

Answer 13

Hydrogen bonding is stronger than van der waals forces

Question 14

State the strongest type of intermolecular force in water and in hydrogen sulfide

Answer 14

Water - hydrogen bonding

Hydrogen sulfide - van der waals forces

Question 15

Explain why the boiling point of water is much higher than the boiling point of hydrogen sulfide

Answer 15

Hydrogen bonding is stronger than van der waals forces

Question 16

Suggest the strongest type of intermolecular force between CCl2F2 molecules

Answer 16

Van der waals forces

Question 17

The boiling point of AsH3 is –62.5 °C and the boiling point of NH3 is –33.0 °C. Suggest why the boiling point of AsH3 is lower than that of NH3

Answer 17

• Weak van der waals forces between molecules of AsH3,
• ammonia has hydrogen bonding,
• van der waals forces is weaker than hydrogen bonding

Question 18

Explain the trend in the boiling points of the hydrogen halides from HCl to HI

HI = 930C
HCL = 400C

Answer 18

• bp increases with the increasing in Mr

- van der waals forces