Polarity/Intermolecular Forces

Question 1

Intramolecular Forces:

Answer 1

A force that holds the atoms within molecules together.

Question 2

Intermolecular Forces:

Answer 2

An electrostatic force of attraction between molecules.

Question 3

Van Der Waals intermolecular forces of attraction:

Answer 3

• Dipole-Dipole
• Dispersion
• Hydrogen

Question 4

Dispersion - Induced Dipoles:

Answer 4

• Occurs in all molecules.
• Significant in non-polar molecules
• Due to random movement of electrons within a molecule, produces varying temporary dipoles making a molecule temporarily polar.
• Dipole on one atom induces dipoles on another atom.

Question 5

Strength of Dispersion Forces:

Answer 5

Strength increases as molecular mass increases - because larger number of electrons.
- Larger molecules have greater melting/boiling point.

Question 6

Dipole-Dipole Attraction (Permanent Dipoles):

Answer 6

• Only in polar molecules.
• Polar molecules experience electrostatic forces of attraction between the dipoles of other polar molecules.

Question 7

Strength of Dipole-Dipole:

Answer 7

• Greater polarity/difference in electronegativity = greater dipole dipole strength
• Which means greater MP and BP.
• Also increases polarity with a greater degree of asymmetry.

Question 8

Hydrogen Bonding:
Extreme form of dipole dipole

Answer 8

• Only in polar molecules.
• Attraction between lone pair of electrons from an F, O, or N atom and a hydrogen atom that is covalently bonded to another F, O, or N atom.
• Small sizes of H,F,N and O concentrates the partial charge in a small volume thus leading to a high charge density.

Question 9

Solubility Of intermolecular forces: (Polar in polar/Non-polar in Non-polar)

Answer 9

-If capable to form complimentary intermolecular forces, they are easily able to form those intermolecular forces between one another.
- Low resistance of mixing these molecules

Question 10

Solubility Of intermolecular forces: (Polar in non-polar) vice versa

Answer 10

• Weak bond

Question 11

Vapour Pressure (kPa)

Answer 11

Measure of the tendency of a substance to vaporise.

Question 12

Relation between intermolecular F and vapour pressure:

Answer 12

Greater intermolecular force = Less vapour pressure Vice versa…

Question 13

What is electronegativity:

Answer 13

Measures the tendency of an atom to attract electrons.
- Increase left to right because of nuclear charge
- Decreases down group electron shielding effect.

Question 14

Polar Covalent:

Answer 14

Between two atoms, electrons are not shared equally because of difference in electronegativity.

Question 15

Polar Molecules:

Answer 15

Have an uneven charge distribution (overall net dipole).

Question 16

Non-polar molecule:

Answer 16

Have an even distribution of charge throughout (Net dipole zero)

Question 17

Net Dipole:

Answer 17

Is the overall movement of electrons.