Intermolecular Forces

Question 1

What is another name for a INTRAmolecular force and where are they found?

Answer 1

• primary bond

* found in bonds within molecules (eg covalent)

Question 2

When you carry out a physical change (melting/boiling), do you break the intramolecular forces or intermolecular forces?

Answer 2

Intermolecular forces. You do not break the covalent bonds

Question 3

What are Coulombic forces and why are they used?

Answer 3

• the attractive and repulsive forces that occur between oppositely charged species and similarly charged species
• to understand intermolecular forces

Question 4

What is Coulomb’s law and what do the symbols stand for?

Answer 4

F=ZAZBe^2/4 π Ɛ0r^2

• F= force
• Za/Zb= charges of ions
• distance
• Ɛ0 is permittivity of a vacuum constant (8.854 x 10 ^-12 J-1 C^2 m^-1)

Question 5

What is the integrated formula of coloumbs law to get U(energy) as the subject?

Answer 5

•U=-ZaZbe^2/4π Ɛ0r

Question 6

Where does coulombic attraction occur?

Answer 6

In the bonding found in ionic solids

Question 7

What is a dipole?

Answer 7

Electrically neutral molecules can be polar or non polar. A polar molecule where there is a dipole

Question 8

What is the dipole equation?

Answer 8

U=ql
U=permanent dipole
q= charge
l= distance between charges

Question 9

How do dipole moments originate?

Answer 9

When there is an electonegativity difference between 2 atoms involved in a bond. They only become appreciable when there is significant ionic character in the bond.

Question 10

What are the units used for dipole moments?

Answer 10

Debye (D)
Columbs (Cm)

1D = 3.33564 x 10 ^-30 Cm
1Cm=2.9979 x 10^29 D

Question 11

How to determine % ionic character?

Answer 11

Experimental value/ theoretical value x 100

Question 12

Units of bond length?

Answer 12

Å

1Å= 1 x 10^-10 m