Intermolecular Interactions

Question 1

What are intermolecular forces and what are they responsible for?

Answer 1

They are attractive forces between molecules and are primarily responsible for the bulk properties of matter (for
example, melting point and boiling point).

Question 2

Which force is much weaker than the other?

Answer 2

Intermolecular forces are much weaker than intramolecular forces.

Question 3

When a molecule has a δ+ and a δ- end then
the molecule is said to be…

Answer 3

polarized or possess a dipole

Question 4

Electronegativity of atoms determine

Answer 4

the sharing of electrons in bonds.

Question 5

The greater the electronegativity…

Answer 5

… the greater the dipole.

Question 6

Diatomic molecules containing the same atoms… (give examples)

Answer 6

have no dipole moment.
e.g. H2, Cl2, O2 = 0 D i.e. NON POLAR

Question 7

Diatomic molecules containing different atoms… (give examples)

Answer 7

may have dipole moments
e.g. HCl, CO, NO > 0 D i.e. POLAR

Question 8

The Dipole moment of polyatomic molecules depends on:

Answer 8

Polarity of the bonds and the shape of the molecule

Question 9

List the types of intermolecular interactions:

Answer 9

1. Dipole - dipole forces
2. Ion - dipole forces
3. Ion - induced dipole forces
4. Dipole - induced dipole forces
5. London dispersion forces
6. Hydrogen bonding.

Question 10

Dipole-dipole interactions occur between…

Answer 10

polar molecules

Question 11

Ion-dipole forces occur between…

Answer 11

an ion and a polar molecule.

Question 12

The strength of the interaction depends on…

Answer 12

the charge and size of the ion and the magnitude of the dipole moment and size of
the molecule.

Question 13

Ion – induced dipole forces & Dipole – induced dipole forces is…

Answer 13

When an ion or polar molecule is placed next to
an atom or nonpolar molecule, the e- distribution
of the atom (or molecule) is distorted by the force of the ion or dipole moment.

Question 14

The extent to which a dipole is induced depends
on:

Answer 14

Charge on ion or size of dipole moment.
Polarizability of atom or non-polar molecule.

Question 15

London dispersion forces are forces in which…

Answer 15

Polarizability enables the creation of
instantaneous dipole moments.

At any instant it is likely that an atom or nonpolar
molecule will have a dipole moment
(instantaneous dipole)

An instantaneous dipole can induce a dipole in
each of its nearest neighbors.

The magnitude of this attractive interaction is
directly proportional to the polarizability of the
atom or molecule.

Question 16

Hydrogen bonds are…

Answer 16

Particularly strong type of intermolecular force. A special type of dipole-dipole interaction between the hydrogen atom in a polar bond, such as N—H, O—H, or F—H, and an electronegative O, N, or F atom.

Question 17

Ion-ion forces are a…

Answer 17

A form of electrostatic force.
Effectively ionic bonding
E.g. NaCl, MgSO4.
Form ionic lattice structures using the electrostatic forces of the fully charged ions.
Ionic interactions take place between many neighbouring ions.
Strong interactions.

Question 18

Give the properties of water and one reason as to why they all exist:

Answer 18

has a high melting and boiling point.
has large surface tension.
is more dense in liquid state than solid state.
has large heat capacity.

All exist due to strength or arrangement of H bonds.

Question 19

Surface tension of water is the amount of…

Answer 19

energy required to stretch or increase
the surface of a liquid by a unit area (for example, by 1 cm^2).

Question 20

Molecules at the surface are pulled ____________ and ___________ by other
molecules, but not upward and away from the surface. This generates surface tension.

Answer 20

downward, sideways

Question 21

Solid form is less dense its liquid form, true or false?

Answer 21

True

Question 22

What are the symptoms of sickle cell anemia?

Answer 22

Narrow capillaries become blocked
The body recognises the sickled cells as abnormal
and destroys them faster than they are replace
Anaemia results

Question 23

The only difference between HbA and sickle cell haemoglobin (HbS) is the substitution of a

Answer 23

negatively charged glutamic acid for a hydrophobic valine.

Question 24

Valine is exposed to ____________________________ and forms a hydrophobic region.

Answer 24

low oxygen concentration

Question 25

Drugs are now designed to target specific sites or receptors. Very often the structure of the drugs are designed to compliment
the site. Often this means creating…

Answer 25

strong intermolecular interactions between drug and target.