Topic 11 Intermoleular fores

Question 1

The increase in volume when converting liquids to gases is

Answer 1

strikingly large

Question 2

in liquid state and solid states,

Answer 2

molecules are packed together almost as tightly in the liquid state as they are in the solid state

Question 3

van der Waals forces (4)

Answer 3

intermolecular forces

include the attractive ad repulsive forces between:

1. molecules with permanent dipoles (dipole-dipole)
2. polar molecules and nonpolar (dipole- induced dipole forces)
3. non polar molecules (induced dipole-induced dipole forces)

Question 4

Explain the role of intermolecular forces on bond energy and why they are important (4)

Answer 4

Although they are about 15% of covalent bond energies, intermolecular forces can have a profound effect on molecular properties such as
- Directly related to boil point, melting point, and the energy needed to convert a solid to a liquid or a liquid to a vaporizer
- important in determining the solubility of gases, liquids and solids in various solvents
- crucial in determining the structure of biologically important molecules such as DNA and proteins

Question 5

polar molecules has

Answer 5

a positive and negative end

Question 6

when a polar molecule encounters a n ionic compound

Answer 6

the neg end of the dipole is attracted to the positive cation and the positive end of the dipole is attracted to the negative anion.

Question 7

Forces of attraction between a positive or neg ion and polar molecules (ion dipole forces) are

Answer 7

less than those for ion-ion attractions but are greater than other types of forces between molecules

Question 8

The attractive forces of an ion dipole depends on (3)

Answer 8

1. The distance between the ion and dipole (closer the stronger the attraction)
2. The charge of the ion (The higher the ion charge=stronger the attraction)

3.The magnitude of the dipole (greater magnitude of the dipole=stronger the attraction)

Question 9

In an ion dipole bond explain the influence of size and ion charge

Answer 9

charge difference has greater effect then the size difference

Question 10

dipole dipole

Answer 10

when a polar molecule encounters another polar molecule of the same or different kind, the positive end of one molecule is attracted to the negative end of the other polar molecule.

Question 11

evaporation

Answer 11

endothermic

Question 12

the greater the forces of attraction between molecules in a liquid…

Answer 12

the greater the energy must be supplied to separate them

Question 13

talk about solubility and polarity

Answer 13

polar molecules are likely to dissolve in a polar solvent and non polar molecules are likely to dissolve in a non polar solvent.

Question 14

Why gasoline and water don’t mix?

Answer 14

the hydrocarbon molecules cannot disrupt the stronger water-water attractions.

Question 15

hydrogen bonding

Answer 15

H bonded to N, O or F are so electrostactically charged due to electronegativity difference that the bond is very strong and polar.

Question 16

Dipole induced Dipole forces