Week 5 IMF

Question 1

What are the 4 types of Intermoolecular forces from lowest to highest strength

Answer 1

1. Dispersion- all molecules and atoms
2. Dipole Dipole- Polar molecules
3. H Bonding- Molecules containign H bonded to N,O,F
4. Ion Dipole- Mixture of ionic compounds and polar compounds

Question 2

Relationships between boiling point/melting point and IMF

Is this inversely or directly

Answer 2

Stronger IMF, more energy needed to overcome these IMF therefore More thermal energy (temp) needed THEREFORE higher boiling and melting points

Directly

Question 3

Dispersion forces

Answer 3

Occurs between all atoms and molecules.
- Instantaneous dipole on a molecule induces another dipole on neighboring molecule.
- Therefore this is the attraction betweeen instantanous and induced dipoles.

Question 4

Dispersion forces

What is polarizability
What factors increase polarizability and explain

Answer 4

Ease of distortion of electron cloud aka how tightly nucleus holds on to electrons
Increased molar mass (electron cloud size) and longer molecules (larger area for interaction) and boiling point

Question 5

Dipole Dipole forces (what areas interact)
What does strength of the dipole depend on

Answer 5

Occurs between polar molecules with permanent dipoles
(negative and positive ends of polar molecules interact)
- Strength depends on magnitude of the dipole moment

Question 6

H Bonding

Answer 6

Occurs between polar molecules with hydrogen atoms covalently bonded to small electronegative atoms (N,O,F) because they have large electronegativity differences

Question 7

What are the 3 aspects of H bonding

Answer 7

1. B bond donor- contributes the H atoms
2. H bond- lone pair of the negative and positive hydrogen end and neighboring polar molecules
3. Hydrogen bond acceptor- Contributes electronegative atom (N,O,F)

Question 8

What are the similaritties and differences of Dipole Dipole and H bonding

Answer 8

Interaction energy is the same/ size of the dipole differs since the size of the dipole in H bonding has larger electronegativirty difference

Question 9

Which boiling point is higher:H2O or H2S and why

Answer 9

H2O because H bonding is stronger than D-D

Question 10

Ion Dipole

Answer 10

Occurs between polar molecules with permanent dipoles and ions (Negative or positve ends of polar molecules and oppositely charged ions attract)

Question 11

Vaporization/heat of vaporization

Answer 11

The process of overcoming IMF to produce change of state from liquid to gas as a result of having sufficient thermal energy
H o Vap:heat required to vaporie one mole of liquid
Endothermic because it requires energy to overcome IMF

Question 12

What factors affect rates of vaporization (increasing)

Answer 12

1. Increasing temp
2. increasing surface area
3. Decrease IMF

Question 13

Temperature and rate of vaporization relationship
Surface area and rate of vaporization (explain)
IMF strength and rate of vaporization

Answer 13

• Increasing temperature increases the rate of vaporization (increased energy to onvercome IMF in liquid)
• Increases surface area increases rate of vaporization as larger surface area, molecules can escape more quickly
• Stronger IMF so lower vaporization rate as stronger IMF require more thermal energy to overcome

Question 14

Volatile

Answer 14

Liquids that vaprorize easily due to weak IMF