Chapter 11

Question 1

intermolecular forces are generally much ____ than bonding forces

Answer 1

weaker

Question 2

Why are intermolecular forces much weaker than bonding forces?

Answer 2

because bonding forces are a result of large charges (protons and electrons) interacting at close distances where as intermolecular forces are a result of smaller charges interacting at greater distances (coulumbs law)

Question 3

What happens when an ion approaches a non-polar atom or molecule?

Answer 3

the negative electron cloud of the nonpolar atom or molecule distorts and the ion induces a small dipole in it

Question 4

define ion-induced dipole forces

Answer 4

a intermolecular force between ions and a nonpolar molecule

Question 5

what is the magnitude of ion-induced dipole forces depend on?

Answer 5

the charge of the ion and how easily the electrons in the atom or molecule can move or polarize in response to the presence of the ion

Question 6

what is the magnitude of the polarizibility of an atom or molecule dependent on (in part)?

Answer 6

the size (or volume) of the electron cloud

Question 7

a larger electron cloud results in a ______ dispersion force because….

Answer 7

greater

the electrons are held less tightly by the nucleus and are therefore easier to polarize

Question 8

define dispersion force (sometimes called the London force)

Answer 8

an intermolecular force exhibited by all atoms and molecules that results from fluctuations in the electron distribution in the absence of an ion

Question 9

what are dispersion forces a result of?

Answer 9

the fluctuations in the electron distribution within atoms or molecules in the absence of an ion

Question 10

what is a temporary or instantaneous dipole?

Answer 10

a temporary dipole caused by electrons being unevenly separated

Question 11

how does an instantaneous dipole affect the atoms around it?

Answer 11

it can induce an instantaneous dipole in the other atoms because of the attraction of the electrons to the positive side of the atom. they then all organize themselves positive to negative

Question 12

what is the magnitude of an instantaneous dipole’s dispersion determined by?

Answer 12

how easily the electrons in the atom or molecule can mover or polarize in response to an instantaneous dipole, which partly depends on the size of the electron cloud.

Question 13

for noble gases, as the number of electrons increases, the volume of the electron cloud _____, and the _____ dispersion forces result in an ______ boiling points

Answer 13

increase
greater
increasing

Question 14

does the number of electrons determine the magnitude of the dispersion force? why?

Answer 14

not alone. shape also affects the dispersion forces (and an atoms boiling point)

Question 15

atoms with larger areas for interaction will have a ______ dispersion force than atoms with smaller areas for interaction

Answer 15

greater

Question 16

define dipole-dipole force

Answer 16

an intermolecular force exhibited by polar molecules that result from the uneven charge distribution

Question 17

what type of molecules have permanent dipoles?

Answer 17

polar molecules

Question 18

define permanent dipole

Answer 18

a permanent separation of charge; a molecule with a permanent dipole always has a slightly negative charge at one end and slightly positive charge at the other

Question 19

the attraction of the postive end of one permanent dipole to the negative end of another permanent dipole is an example of which force?

Answer 19

dipole-dipole force

Question 20

due to dipole-dipole forces polar molecules have a ______ melting point than non polar molecules with a similar number of electrons or of similar size

Answer 20

higher

Question 21

do all molecules have dispersion forces?

Answer 21

yes

Question 22

define miscibility

Answer 22

the ability to mix without separating into two phases

Question 23

in general polar liquids _____ miscible with other polar liquids and _____ miscible with non polar liquids

Answer 23

are

are not

Question 24

define hydrogen bonding

Answer 24

a strong type of intermolecular bonding that occurs between polar molecules that contain hydrogen atoms bonded directly to small electronegative atoms (like O, F, or N)

Question 25

as a result of the large partial postive and negative charge on a fairly small atom there is a ____ attraction between the H atom in one molecule and the O, F, or N in its neighbour. This is called….

Answer 25

strong

a hydrogen bond

Question 26

hydrogen bonds are not to be confused with chemical bonds. hydrogen bonds occur due to…

Answer 26

intermolecular forces between molecules

Question 27

hydrogen bonds are _____ than a typical covalent bond

Answer 27

weaker

Question 28

weak hydrogen bonds are _____ than the weakest dispersion and dipole-dipole forces, but the strongest dispersion forces can be as strong as what are considered to be the strongest hydrogen bonds

Answer 28

stronger

Question 29

define dipole-induced dipole force

Answer 29

an intermolecular force between molecules that have a permanent dipole and an atom or molecule that is non polar

Question 30

when a non polar atom or molecule and a molecule with a permanent dipole approach one another what happens?

Answer 30

the negative or positive end of the polar molecule distorts or polarizes the electron cloud of the non polar atom or molecule. Then because the non polar atom or molecule has a small induced dipole it can interact with the polar molecule.

Question 31

what does the magnitude of the dipole-induced dipole force depend on?

Answer 31

the size of the dipole of the polar molecule and the polarizability of the non polar atom or molecule

Question 32

define ion-dipole force

Answer 32

an intermolecular force between an ion and the oppositely charged end of a polar molecule

Question 33

when do ion-dipole forces occur?

Answer 33

when an ionic compound is mixed with a polar compoud; it is especially important in aqueous solutions of ionic compounds

Question 34

When thermal energy is high relative to intermolecular forces, matter tends to be ______.

Answer 34

Gaseous

Question 35

When thermal energy is low relative to intermolecular forces, matter tends to be _____ or _____

Answer 35

Liquid or solid

Question 36

Define crystalline

Answer 36

???

Question 37

Molecules with partial or temporary charges are attracted to each other because their ____ ____ decreases they get closer together

Answer 37

Potential energy

Question 38

For hydrogen bonding what are the most important small electronegative atoms?

Answer 38

Fluorine, oxygen, nitrogen

Question 39

Why have a higher boiling point than accounted for by the trend for hydrides?

Answer 39

Because Water has two lone pairs to accept hyrdorgen bonds and two O-H bonds to act as donors. Therefore water can participate in 4 hydrogen bonds simultaneously

Question 40

Ion-dipole forces can be very ___ and are especially important in aqueous solutions of _____ ____

Answer 40

Strong

Ionic compounds

Question 41

why does a larger electron cloud cause the dispersion force to be greater?

Answer 41

because the electrons are held less tightly around the nucleus and therefore are distorted or polarized more easily

Question 42

if all other variables are constant, the dispersion force increases with _____ number of electrons which typically ____ the size of the electron cloud

Answer 42

increasing

increases

Question 43

dipole-dipole forces exist in ____ polar molecules

Answer 43

all