Intermolecular Forces

Question 1

What are the 3 intermolecular forces we discuss in this class, from strongest to weakest?

Answer 1

1. Hydrogen bond
2. Dipole
3. Dispersion

Question 2

What is an intermolecular bond?

Answer 2

Bond formed between molecules.

Question 3

What causes a dipole to form?

Answer 3

Electrostatic forces

Question 4

What are the type of molecules that form dipoles?

Answer 4

Polar molecules

Question 5

What does the separation of charge that occurs on polar molecules play in forming dipoles?

Answer 5

The opposite charges attract, causing the sharing of electrons between these molecules at the oppositely charged regions.

Question 6

Is an H-bond a type of dipole?

Answer 6

YES

Question 7

H-bonds are really strong only when considering?

Answer 7

Intermolecular bonds

NOT intramolecular bonds.

Question 8

What are the three highly electonegative atoms (HEA) that can be covalently bound to hydrogen in order to form a hydrogen bond?

Answer 8

Nitrogen

Fluorine

Oxygen

Question 9

What shape must the HEA and the bound hydrgen have in order to form hydrogen bond?

Answer 9

Linear

Question 10

What is the only reason that liquid water exists?

Answer 10

Because of hydrogen bonds.

Question 11

Normally the higher the mass of the molecule, the higher the boiling point, but what makes water so special that it has a higher boiling point than molecules that are heavier than it?

Answer 11

It’s hydrogen bonds.

Question 12

How do trees and DNA use hydrogen bonds?

Answer 12

Trees use hydrogen bonds to help water get from roots all the way to their leaves by being able to form a chain through hydrogen bonds that helps to work against gravity.

DNA uses hydrogen bonds to hold its antiparallel strands together and also is just weak enough to allow them to break apart for the replication process when needed.

Question 13

What types of molecules use dispersion?

Answer 13

nonpolar molecules.

Question 14

Describe the intermolecular force of dispersion.

Answer 14

Electrons move back and forth around the molecule and will temporarily cluster.

Partial charge will wax and wane as they move, these are called DIPOLE MOMENTS.

Sometimes change can be neutral as electrons moves and there will be no force present.

Question 15

Is it to be assumed that molecules will always make the strongest bond between each other that they possibly can?

Answer 15

YES

Question 16

What two intermolecular bonds can be formed with polar molecules?

Answer 16

Dipole

H-Bond

Question 17

If a molecule is polar, how do you determine that an H-bond can be formed versus a regular dipole?

Answer 17

Is there a HEA? (NOF)

Is there hydrogen?

Is the hydrogen bonded to the HEA? (might have to draw lewis dot structure)

Question 18

Do ionic, covalent, or both types of molecules use intermolecular forces?

Answer 18

ONLY COVALENT