Weeks 8 & 9 - Intermolecular Forces & Chemical Equilibrium

Question 1

What are intermolecular forces?

Answer 1

Are attractive forces between molecules.

Question 2

What are dipole-dipole forces?

Answer 2

Attractive forces between the positive end of one polar molecule and the negative end of another polar molecule.
The larger the dipole moment, the greater the force

Question 3

What are dipole-induced dipole forces?

Answer 3

A molecule with a permanent dipole induces a dipole in a neighbouring molecule.

Question 4

What is an ion-dipole force?

Answer 4

An attractive force that results from the electrostatic attraction between an ion and a neutral molecule that has a dipole.
Cation attracts partially negative end of neutral polar molecule.
Anion attracts partially positive end of neutral polar molecule.

Question 5

What is the definition of polarizability?

Answer 5

How easily the electron distribution in the molecule or atom can be distorted.

Question 6

Explain the Van der Waals forces.

Answer 6

Are the residual attractive or repulsive forces between molecules or atomic groups that do not arise from a covalent bond, or electrostatic attraction of ions or of ionic groups with one another or with neutral molecules.
Forces can be attractive or repulsive.

Question 7

What is a dispersion force?

Answer 7

A force between molecules or atoms, arising from a brief shift of orbital electrons to one side of the atom or molecule resulting of a temporary dipole induced in atoms or molecules

Question 8

What occurs in hydrogen bonds?

Answer 8

A special dipole-dipole interaction between the hydrogen atoms in a polar bond, (H-FON), and the lone pair of an electronegative O, N or F atom

Question 9

What is fluid surface tension?

Answer 9

The elastic force in the surface, results from the greater attraction of liquid molecules to each other (cohesion).
Strong intermolecular forces = high surface tension.

Question 10

What is cohesion?

Answer 10

Is the intermolecular attraction between like molecules.

Question 11

What is adhesion?

Answer 11

Is an attraction between unlike molecules

Question 12

What is viscosity?

Answer 12

A measure of a resistance to flow- high intermolecular forces= high viscosity.
Bonds between molecules must be broken to allow molecules to move past each other

Question 13

What is a metallic bond?

Answer 13

Arises from the electrostatic force between conduction electrons and positively charged metal ions

Question 14

What is a phase change?

Answer 14

A physical change as a result of changes in molecular order. Usually heat or energy transfer

Question 15

What is the phase change from liquid to gas?

Answer 15

Vaporisation

Question 16

What is the phase change from gas to liquid?

Answer 16

Condensation

Question 17

What is the phase change from liquid to solid?

Answer 17

Freezing.

Question 18

What is the phase change from solid to liquid?

Answer 18

Melting.

Question 19

What is the phase change from solid to gas?

Answer 19

Sublimation

Question 20

What is the phase change from gas to solid?

Answer 20

Deposition

Question 21

What is equilibrium liquid vapour pressure?

Answer 21

The pressure exerted by a vapour in equilibrium with its condensed phases at a given temp (at equilibrium with the atmosphere outside it)

Question 22

What is liquid vapour pressure?

Answer 22

The pressure exhibited by vapour above a liquid surface.

Question 23

Describe condensation.

Answer 23

As the concentration of molecules in the vapour phase increases, some molecules condense and return to the liquid phase.
Occurs when molecules collide with the surface of the liquid and become trapped by intermolecular forces.

Question 24

What is a dynamic equilibrium?

Answer 24

Exists once a reversible reaction ceases to change its ratio of reactants/ products, but substances move between the chemicals at an equal rate, there is no net change

Question 25

What is chemical equilibrium?

Answer 25

A mixture of both reactants and products - the chemical composition of a system does not change with time.

Question 26

What is the equilibrium constant?

Answer 26

K - the value of the equilibrium constant expression when the system is at equilibrium.

Question 27

Describe Le Chatelier’s principle.

Answer 27

If an outside influence upsets an equilibrium, the system undergoes a change in a direction that counteracts the disturbing influence and, if possible, returns the system to equilibrium.

When any system at equilibrium is subjected to change in concentration, temperature, volume or pressure, the system will readjust itself to counteract the effect of the applied change to establish a new equilibrium.