Intermolecular forces

Question 1

where can you find intermolecular forces?

Answer 1

between covalent bonds

Question 2

where are intramolecular forces?

Answer 2

inside each molecule

Question 3

what are intermolecular forces?

Answer 3

the attractions between molecules

Question 4

3 types of intermolecular forces

Answer 4

dipole dipole attraction
Van der waal attraction
hydrogen bonds

Question 5

strength of Van der waal attraction

Answer 5

weakest

Question 6

strength of dipole dipole attraction

Answer 6

medium strength

Question 7

strength of hydrogen bonds

Answer 7

strongest

Question 8

when does dipole-dipole attraction happen?

Answer 8

when a covalent molecule has permanent partial + and partial - charges due to having large electronegativity differences

Question 9

where do van der waal forces occur

Answer 9

do not have dipole moments, non-polar covalent

Question 10

what causes van der waal forces?

Answer 10

flickering dipoles

Question 11

what causes flickering dipoles

Answer 11

due to their random movement within the orbitals, there are small lengths of time when the electrons are not equally shared

Question 12

what does it mean for a flickering dipole to be ‘on’

Answer 12

inducing a temporary dipole

Question 13

what point in time do van der waal forces occur

Answer 13

when the 2 molecules involved are both ‘on’

Question 14

why does NO boil at much higher than N2

Answer 14

because van der waal forces are much weaker than dipole-dipole attraction

Question 15

why does boiling point increase with Mr in non-polar covalent molecules

Answer 15

because the number of van der waal forces increases with Mr

Question 16

what causes the great strength of polythene?

Answer 16

it is due to millions of van der waal forces betwee the parallel molecules

Question 17

boiling points of hydrogen bonding

Answer 17

surprisingly high BP

Question 18

when does a hydrogen bond occur?

Answer 18

when hydrogen in a covalent bond with N,O or F in one molecule AND there is a lone pair of electrons on either N,O or F on another neighbouring molecule

Question 19

example of hydrogen bonding

Answer 19

in water

Question 20

why are N,O and F significant in hydrogen bonding (2)

Answer 20

1. very high electronegativity values

2. smallest atomic radii

Question 21

why is Cl not involved in hydrogen bonding

Answer 21

atomic radius is too bigh

Question 22

how much stronger is a covalent bond than a hydrogen bond

Answer 22

10 times stronger

Question 23

where do you find hydrogen bonding between N and O

Answer 23

in biology; proteins, DNA etc.

Question 24

why is ammonia extremely soluble in water?

Answer 24

becuase of hydrogen bonding

Question 25

why does water expand below 4ºC?

Answer 25

when water is about the solidify as ice, H2O molecules rotate so that they can have their maximum of 4 H bonds, for this they need more "elbow room"

Question 26

why is the boiling point of water much higher than that of NH3 or NF?

Answer 26

there is not the maximum aof 4 hydrogen bonds in them as opposed to in water

Question 27

4 properties hydrogen bonding gives water

Answer 27

High BP affects density skin on water clustering

Question 28

explain high BP of water

Answer 28

very high BP for a its Mr of 18

Question 29

explain how h bonding affects density

Answer 29

solid form less dense that liquid form

Question 30

explain the skin of the water

Answer 30

water molecules attracted to each other and causes surface tension

Question 31

why does like dissolve like

Answer 31

polar solutes dissolve in polar solvents because they are both charged etc.

Question 32

All other things being equal, boiling point increases...

Answer 32

boiling point increases with Mr

Question 33

what gives shapes of covalent molecules?

Answer 33

Valence Electron Repulsion Theory

Question 34

2 things that the Valence Electron Repulsion Theory states

Answer 34

i) Electron pairs repel each other so that they end up as far apart from each other as is possible in space ii) Lone pairs are better at repelling than bonded pairs

Question 35

why are lone pairs are better at repelling than bonded pairs ?

Answer 35

they are closer to the nucleus of the central atom

Question 36

What gives the name of the shape of a molecule?

Answer 36

the number of electron pairs (lone or bonded) on the outer shell of the central atom

Question 37

3 steps to determine the shape of a molecule question

Answer 37

1. is it ionic or covalent 2. draw ring diagram of molecule 3. count number of electron pairs on the outer shell of the central atom

Question 38

2 electron pairs on outer shell of central atom

Answer 38

linear

Question 39

bond angle of linear molecule

Answer 39

180º

Question 40

example of linear molecule

Answer 40

BeH2

Question 41

3 electron pairs on outer shell of central atom

Answer 41

triagonal planar

Question 42

bond angles in triagonal planar molecule

Answer 42

120º

Question 43

example of triagonal planar molecule

Answer 43

BF3

Question 44

4 bonded electron pairs on outer shell of central atom

Answer 44

perfect tetrahedral

Question 45

bond angle of perfect tetrahedral molecule

Answer 45

109.5º

Question 46

example of perfect tetrahedral molecule

Answer 46

CH4

Question 47

3 bonded and 1 lone pair of electron pairs on outer shell of central atom

Answer 47

pyramidal

Question 48

bond angle of pyramidal molecule

Answer 48

107º

Question 49

example of pyramidal molecule

Answer 49

NH3

Question 50

2 bonded and 2 lone pairs of electrons on outer shell of central atom

Answer 50

V-shaped

Question 51

bond angle in v-shaped molecule

Answer 51

105º

Question 52

example of v-shaped molecule

Answer 52

H2O

Question 53

tetrahedral angle in NH3

Answer 53

107º

Question 54

why is tetrahedral angle in NH3 107º?

Answer 54

lone pair - bonded pair repulsion is greater than bonded pair - bonded pair repulsion

Question 55

tetrahedral angle in H2O

Answer 55

105º

Question 56

why is the tetrahedral angle in H2O 105º?

Answer 56

lone pair - lone pair repulsion is greater than lone pair - bonded pair repulsion which is greater than bonded pair - bonded pair repulsion

Question 57

diatomic molecules shape

Answer 57

linear

Question 58

3 examples of diatomic molecules

Answer 58

H2, O2, N2

Question 59

Shape of carbon with 4 single bonds

Answer 59

tetrahedral

Question 60

shape of carbon with one double or triple bond

Answer 60

planar