Exam I

Question 1

What can we assume from the presence of a lone pair in a molecule?

Answer 1

There will be an unequal distribution of polarity, which will make the molecule behave in an unique way.

Question 2

What are intramolecular forces?

Answer 2

They are forces within a molecule. Examples are ionic, and covalent.

Question 3

What are intermolecular forces?

Answer 3

They are forces between molecules. Examples are London forces (dispersion), dipole-dipole, and Hydrogen bonding.

Question 4

Where can we find dispersion forces?

Answer 4

All molecules

Question 5

Where can we find dipole-dipole forces?

Answer 5

They are found in all polar molecules, which will present higher BP and MM than molecules of similar MM that are not polar

Question 6

Where can we find hydrogen bonds?

Answer 6

In all polar molecules with H bonds to F, O, and N. It is basically a dipole-dipole, but generally stronger

Question 7

Dipole-dipole is the strongest force.

Answer 7

False; it is hydrogen bonding. However dipole-dipole is still strong, as they are permanent

Question 8

Intermolecular forces only exist between molecules with ionic bounds.

Answer 8

False. Intermolecular forces exist between all substances

Question 9

Intermolecular forces will ___________ properties of a substance such as _____________, ______________, _____________, and others.

Answer 9

Dictate, boiling point, freezing point, vapor pressure

Question 10

How do gases, liquids, and solids differ?

Answer 10

In the freedom of movement of their constituent parts.

Question 11

What is the direction of energy when a phase changes from solid to gas?

Answer 11

Endothermic

Question 12

What is the direction of energy when a phase changes from gas to solid?

Answer 12

Exothermic

Question 13

Intermolecular forces determine ________ energy is released or absorbed (defined by ______)

Answer 13

How much, delta H

Question 14

The stronger the IMF, the lower the temperature needed to overcome them.

Answer 14

False. The higher the temperature has to be in order to overcome them.

Question 15

What are the main differences between a crystalline and an amorphous substance?

Answer 15

Crystalline substances are regular, ordered, and have a long-term pattern; amorphous substances are still compact but without the long term order.

Question 16

Intermolecular forces are ________ in nature

Answer 16

Attractive

Question 17

Every substance will experience some level of dispersion forces; they are called _____________ or temporary, because they can be ________.

Answer 17

Instantaneous; induced

Question 18

The magnitude of the dispersion forces is a result of…

Answer 18

How easily the substance can be polarized

Question 19

The strenght of the IMF also depends on the surface area, therefore as branch reduces, IMF reduces as well.

Answer 19

False. As branching increases, IMF reduces

Question 20

What can we assume from the presence of dipole-dipole forces?

Answer 20

That the positive end of one molecule is attracted to the negative end of the other.

Question 21

Because dipole-dipole represents a shift in the electron density within a substance…

Answer 21

There will be an e rich region and an e poor region in that molecule. The more the IMF increases, the more the dipole moment increases as well.

Question 22

What is miscibility?

Answer 22

It is the ability that one substance has to dissolve like substances.

Question 23

When do we see hydrogen bonding?

Answer 23

In polar molecules where H is connected DIRECTLY to O, F, and N. Therefore, if hydrogen is bonding to a carbon that is bondind to an oxygen, it is not hydrogen bonding.

Question 24

What is the order of the IMF’s in order of strenght?

Answer 24

Dispersion forces - Dipole-dipole - Hydrogen bonding

Question 25

Molecules that have hydrogen bonding have generally lower boiling points

Answer 25

False. They have higher boiling points because the attraction between the molecules is high, therefore it requires more energy to separate them.

Question 26

What molecule has all three types of IMF's?

Answer 26

Water

Question 27

When can we find ion-dipole forces?

Answer 27

These forces are present when ions interact with molecular substances

Question 28

What is surface tension?

Answer 28

It is the energy needed to increase the surface area of a liquid.

Question 29

Surface tension cannot be altered

Answer 29

False. Surface tension can be altered by adding other substances into the liquid like soap for example.

Question 30

What is viscosity?

Answer 30

It is the resistance of a liquid to a flow. Generally, the higher the IMF, the higher the viscosity. Viscosity can be affected by the molecular shape, branching, or temperature

Question 31

What is capillary rise?

Answer 31

It is the natural behavior of a liquid raising on a column; it explains the meniscus shape we see when measuring liquids in a lab.

Question 32

What are adhesive forces?

Answer 32

They lead unlike substances to stick together

Question 33

What are cohesive forces?

Answer 33

They lead like substances to stick together.

Question 34

In H20, ____________ are stronger than \_\_\_\_\_\_\_\_\_\_\_; in Hg, ____________ are weaker than \_\_\_\_\_\_\_\_\_\_\_\_\_\_.

Answer 34

Adhesive, cohesive, adhesive, cohesive

Question 35

Phases changes occur during peaks of temperature.

Answer 35

False; phase changes occur at a constant temperature. The energy during a phase change is put in the transition between the phases instead of being used to change the temperature.

Question 36

What is the heat of vaporization?

Answer 36

Amount of heat required to vaporize 1 mole of a substance. The formula reads Delta H vaporization = - Delta H condensation. Delta H vaporization is endothermic, and delta H condensation is exothermic.

Question 37

Rate of evaporation = rate of condensation (dynamic equilibrium)

Answer 37

Vapor pressure

Question 38

Which state of matter is compressible?

Answer 38

Gas

Question 39

Transition between liquid and solid can also be induced by what?

Answer 39

Changes in pressure

Question 40

Gases can be condensed by...

Answer 40

Decreasing temperature or increasing pressure

Question 41

Which halogen has the highest boiling point?

Answer 41

I2

Question 42

What alcohol also presents all three IMF's?

Answer 42

Ethanol

Question 43

The weaker the attractive forces, the higher the vapor pressure.

Answer 43

True

Question 44

What is the relationship between external pressure and boiling point?

Answer 44

They are directly related; the lower the external pressure, the lower the boiling point.

Question 45

What is the temperature required to produce a supercritical fluid?

Answer 45

Critical temperature

Question 46

What is the pressure at the critical temperature called?

Answer 46

Critical pressure

Question 47

Vaporization is an ______________ process, therefore it is \_\_\_\_\_\_\_\_\_\_\_, while condensation is an ______________ process, therefore, it is \_\_\_\_\_\_\_\_\_\_\_\_\_.

Answer 47

Endothermic, positive, exothermic, negative

Question 48

Cappilary action involves adhesive and cohesive forces

Answer 48

True

Question 49

Viscosity of a liquid ___________ as the temperature increases

Answer 49

Decreases

Question 50

When adding a solute to a solution, no changes are noticed in the properties of the solution.

Answer 50

False; the interferences decreases the freezing point and increases the boiling point

Question 51

A colligative property depends on the identity of the solute

Answer 51

False. It depends on the concentration of the solute and not on its identity

Question 52

The boiling point of a siolution is __________ than the pure solvent, and its freezing point is _______________ than the pure solvent.

Answer 52

Higher, lower

Question 53

What state of matter is held together with relatively high IMF's?

Answer 53

Solid

Question 54

In the polar substance CH2O, what IMF's are present?

Answer 54

Dispersion, dipole-dipole

Question 55

How many hidrogen bonds can a single water molecule participate in?

Answer 55

4

Question 56

What happens if an additional solid solute is added to an unsaturated solution?

Answer 56

The solute goes into solution

Question 57

What happens if addition solid solute is added to a saturated solution?

Answer 57

The solute remains an undissolved solid