Intermolecular Forces

Question 1

What are the 2 types of attraction in molecules?

Answer 1

Intramolecular and intermolecular forces.

Question 2

What are intramolecular forces?

Answer 2

Forces of attraction within a molecule or ionic compound. (Holds atoms and ions together)

Question 3

What are intermolecular forces?

Answer 3

Forces of attraction between molecules.

Question 4

Which of INTRA and INTER mfs are stronger?

Answer 4

Intras are stronger.

Question 5

What is happening when you boil water?

Answer 5

You are breaking the intermolecular forces.

Question 6

Breaking the intermolecular forces does what?

Answer 6

Changes state.

Question 7

What are the 3 kinds of intermolecular forces in order from weakest to strongest?

Answer 7

vanderwaals, dipole-dipole, H-bonds.

Question 8

What are Vanderwaal’s forces?

Answer 8

Attractions between molecules that have temporary dipoles.

Question 9

What are dipole-dipole forces?

Answer 9

Attractions between molecules that have permanent dipoles.

Question 10

What is hydrogen bonding?

Answer 10

Attractions between molecules that contain very strong dipoles (H with N, O, or F).

Question 11

Which intermolecular force occurs in all molecules.

Answer 11

Vanderwaals.

Question 12

Why and how do Vanderwaals occur?

Answer 12

Because the electrons are moving around in atoms, so there will be instants when the charge around an atom is not symmetrical. This makes tiny dipoles which cause attraction between neighbouring atoms/molecules.

Question 13

What factor increases the strength of Vanderwaals?

Answer 13

Size. Larger molecules have more protons and electrons.

Question 14

Do larger molecules have higher or lower boiling points?

Answer 14

Higher

Question 15

In a hydrocarbon chain, how does the number of carbons affect the boiling point?

Answer 15

As the number of carbons increase, the boiling point also increases.

Question 16

How do Vanderwaals affect the halogens?

Answer 16

As you go down the halogens, their molar mass increases. This means they have more electrons and are harder to separate (higher boiling point).

Question 17

What are 2 reasons why vanderwaals forces increase as molar mass increases?

Answer 17

With the molar mass, the number of electrons and the radius of the atom increase. The more electrons you have, and the more distance over which they can move, the bigger the possible temporary dipoles.

Question 18

Why and how do dipole-dipole forces occur?

Answer 18

Polar substances have a slightly electronegative end and a slightly electropositive end. Dipole-dipole forces occur when oppositely charged poles momentarily attract one another.

Question 19

What is the only intermolecular force that non-polar molecules have?

Answer 19

Vanderwaal

Question 20

How does the electronegativity difference of the dipole moment affect the forces of attraction (dipole-dipole).

Answer 20

Greater EN means stronger dipole-dipole forces and higher boiling point.

Question 21

Order HCl, HBr, and HI from highest boiling point to lowest.

Answer 21

HCl, HBr, HI

Question 22

Why and how does hydrogen bonding occur?

Answer 22

N, O, and F are highly electronegative and have lone pairs of electrons which are attracted to H atoms in neighbouring molecules.

Question 23

The hydrogen atoms in neighbouring molecules are essentially what?

Answer 23

Protons because of uneven sharing of the electron pair between H and NOF.

Question 24

WHy are hydrogen bonds the strongest?

Answer 24

Because they have a much greater electronegativity than Dipole dipole forces.

Question 25

How much stronger are Hydrogen bonds vs dipole dipole?

Answer 25

5 times stronger

Question 26

What is misleading about the name “hydrogen bonding”?

Answer 26

It is not a real bond, since it is between molecules.

Question 27

Out of COH, CCOH, and CCCOH, which is the most polar?

Answer 27

COH, because C is NP and OH is P. As the Carbon chain increases, the non-polar region becomes more significant, making the molecule less polar.

Question 28

What is affected by the strength of IMFs between neighbouring covalent molecules?

Answer 28

The molecules’ boiling and melting points.

Its solubility in polar or nonpolar solvents.

Question 29

When sharing electrons with H, what happens to the boiling point as you go down the group?

Answer 29

The molecule becomes stronger and has a higher boiling point. EXCEPTION: Even though O is the first in the group, H2O has the highest boiling point, because it has the ability to form H-bonds.

Question 30

Why does the boiling point increase down a group (as period increases) ?

Answer 30

Electronegative difference and SIZE increase. Larger size means greater vanderwaals.