Chemistry Exam 1: Chapter 10

Front 1

In which phase are attractive forces so strong that particles are held close together and unable to move (rigid)?

Back 1

solids

Front 2

In which phase are attractive forces weak and allow particles to be far apart and free to move?

Back 2

gases

Front 3

In which phase are attractive forces strong enough to hold particles close together but still allow them to move?

Back 3

liquids

Front 4

In which phase are particles held in an ordered arrangement?

Back 4

solids

Front 5

What is the most electronegative element?

Back 5

Flourine (F) - 4.0

Front 6

When are polar covalent bonds formed?

Back 6

when there are two elements with a difference in electronegativity

Front 7

What does the point of a dipole arrow represent?

Back 7

the element in the bond that is more electronegative, which is represented by a (-) charge

Front 8

What does the crossed end of a dipole arrow represent?

Back 8

the element in the bond that is less electronegative, which is represented by a (+) sign (hint: crossed end resembles a plus sign)

Front 9

Why is Chlorine more electronegative than Carbon?

Back 9

because it is further along across the row on the periodic table

Front 10

What type of bond is an electrostatic attraction between opposite charges?

Back 10

ionic bond

Front 11

What type of bond is the equal or unequal sharing of electrons?

Back 11

covalent bond

Front 12

What determines if a molecule is polar?

Back 12

determine which bonds are polar (electronegativity differences)

use the shape of the molecule to see if dipoles cancel

IF dipoles cancel, the molecule is nonpolar.

Front 13

Why is CO2 nonpolar?

Back 13

O=C=O
the electronegativity between O (3.5) and C (2.5) is higher than 0.3, but the shape is linear. Therefore dipoles cancel, making the molecule nonpolar.

Front 14

If a molecule has a larger electronegativity difference, it will also have larger ________ movement.

Back 14

dipole

Front 15

What term describes attractive forces between molecules that hold them together?

Back 15

intermolecular forces

Front 16

What term describes bonding forces from covalent bonds?

Back 16

intramolecular forces (within the molecule)

Front 17

Molecules with dipole-dipole have higher ________ ______.

Back 17

boiling points

Front 18

A molecule with the element Boron (B) will likely have what shape?

Back 18

trigonal planar

Front 19

A molecule with the element Carbon (C) will likely have what shape?

Back 19

tetrahedral

Front 20

Why are London dispersion forces present in all atoms and molecules?

Back 20

because all molecules have electrons in "clouds" outside of the nucleus; LDF result from the motion of electrons

Front 21

How can it be determined that one molecule has a higher boiling point than another by looking at size?

Back 21

larger molecules = larger polarizability (squishiness) = increased LDF
increased LDF = higher boiling point

Front 22

CH bonds are assumed to always be ________.

Back 22

nonpolar

Front 23

How does LDF depend on shape?

Back 23

increased surface area of rod-like shapes = increased LDF
thus rod-like shapes have a higher boiling point

Front 24

What is a hydrogen bond?

Back 24

an attraction of Hydrogen with a very electronegative atom (N, O, or F); highly polar; unusually strong bond; has extremely high boiling point

Front 25

Why do NH3, H2O, and HF have higher boiling points than expected?

Back 25

because of the hydrogen bonds they contain

Front 26

What is viscosity?

Back 26

thickness; stickiness

Front 27

How do IMF affect viscosity?

Back 27

larger IMF = more viscosity

Front 28

How do IMF affect surface tension?

Back 28

larger IMF = larger surface tension

Front 29

Which phase changes absorb heat (endothermic reaction) to overcome the intermolecular forces holding molecules together?

Back 29

MELTING solid --> liquid
SUBLIMATION solid--> gas
VAPORIZATION liquid --> gas

Front 30

Which phase changes release heat (exothermic reaction) to make intermolecular forces hold particles more tightly together?

Back 30

FREEZING liquid--> solid
DEPOSITION gas --> solid
CONDENSATION gas --> liquid

Front 31

How do IMF affect vapor pressure?

Back 31

smaller IMF = larger vapor pressure

Front 32

What is the strength of london dispersion forces?

Back 32

weakest (1-10 kJ/mol)

Front 33

What is the strenght of dipole-dipole forces?

Back 33

weak (3-4 kJ/mol)

Front 34

What is the strength of hydrogen-bonding forces?

Back 34

moderate (10-40 kJ/mol)

Front 35

What is the strength of ion-dipole forces?

Back 35

strongest, yet moderate (10-50 kJ/mol)

Front 36

In order to increase the rate of vaporization, one must...

Back 36

increase temperature
increase surface area (because loosely held molecules escape more easily)
decrease amount of intermolecular forces

Front 37

What is the critical point on a phase diagram?

Back 37

the point where there ceases to a boundary between phases and supercritical fluid is produced

Front 38

What is the triple point on a phase diagram?

Back 38

the point where a substance is a solid, liquid, and gas all at once

Front 39

How many ions are in a corner atom?

Back 39

1/8

Front 40

How many ions are in a center atom?

Back 40

1

Front 41

How many ions are in a face atom?

Back 41

1/2

Front 42

How many ions are in a edge atom?

Back 42

1/4

Front 43

Is CH4 polar or nonpolar?

Back 43

CH4 is nonpolar due to its tetrahedral structure, which is very symmetrical. The "H" molecules are equal in electronegativity and are each pulling the "C" in opposite directions, thus making the compound nonpolar.

Front 44

When is a compound considered ion-dipole?

Back 44

the bond must be ionic, polar, and be in water (aq)

Front 45

Which bond has the higher boiling point? CH3OH or CH3SH

Back 45

CH3OH due to Hydrogen-bonding

Front 46

Which bond has the higher boiling point? CH4 or CH3Cl

Back 46

CH3Cl due to dipole-dipole interaction; CH4 is nonpolar

Front 47

Which bond has the higher boiling point? NF3 or CH4

Back 47

NF3 due to hydrogen-bonding

Front 48

Dispersion forces ________ down a group due to size.

Back 48

increase

Front 49

What term describes the ability of liquids to flow against gravity up a narrow tube?

Back 49

capillary action

Front 50

What is cohesion?

Back 50

attraction to itself (e.g. mercury)

Front 51

What is adhesion?

Back 51

attraction of a molecule to surface of tube (e.g. water)

Front 52

Describe enthalpy.

Back 52

ΔS (+) heat in (+)

Front 53

Describe entropy.

Back 53

ΔS (-) heat out (-)