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physical chem > how molecules stick together > Flashcards

how molecules stick together Flashcards

1
Q

how do molecules have linear shapes

A

if bonding pairs are in negative charge cloud because electrons repel each other and move away from each other as far as possible

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2
Q

shapes of molecules with 2 electron pairs

A

linear shape

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3
Q

bond angle

A

angle between 2 bonds to identify same shaped molecules

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4
Q

bond angle of linear shapes

A

180

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5
Q

molecules name and shape and angle with 3 bond pair electrons

A

-trigonal planar
120 degrees

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6
Q

molecules name and shape with 4 electron pairs

A

109.5 degrees
tetrahedral

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7
Q

ammonia bond angle

A

107

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8
Q

bond angle in water

A

104.5

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9
Q

bond angle when there is lone pair with bond pair

A

bond angle decreases

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10
Q

why does bond angle decrease with lone pair and bond pair

A

lone pair charge cloud wider than bond pair charge cloud
-repel more than bonding pairs
-distance between bonding pairs decreases

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11
Q

order of electron pair repulsion biggest to smallest

A

lone pair lone pair
lone pair bond pair
bond pair bond [air

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12
Q

VESPR

A

valence electron shell repulsion theory
-predicting shapes of molecules

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13
Q

molecule with 2 bonding pairs and one lone pair

A

shape is bent
angle 118

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14
Q

molecule with 3 bond pairs and 1 lone pair

A

shape trigonal pyramidal
bond angle 107

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15
Q

water with 2 bonding pairs and lone pairs shape and angle

A

-bent
angle 104.5

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16
Q

molecule with 5 electron bonding pairs shape and angle

A

trigonal bipyrymidal
-120 and 90

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17
Q

molecule with 4 bonding pairs and 1 lone pair

A

-seesaw FML
-100 and 85

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18
Q

molecule with 3 bonding pairs and 2 lone pairs

A

t shaped
88 degrees

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19
Q

molecule with 3 bonding pairs and 2 lone pairs shape and angle

A

linear
180

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20
Q

molecule with 6 bonding electron pairs

A

-90 degrees
octahedral

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21
Q

molecule with 4 bonding pairs and 2 lone pairs

A

-lone pairs opposite
-90
-square planar

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22
Q

predicting shape of molecule when electron pairs not given

A

-electron pairs repel as much as possible
-draw dot and cross
count how many electron pairs bonding and lone
-identify shape
-add atoms and lone pairs

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23
Q

shapes of molecules with double bonds

A

-double bonds dont repel each other
linear arrangement
-180

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24
Q

how to know if molecule polar

A

if polar bonds
dipole
so molecule polar
bonds on same side of molecule

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25
Q

what happens if bonds not on same side of molecule

A

-dipoles cancel oout when following vectors of bond charges

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26
Q

if all atoms around central atom all same polar or not

A

if all same molecule non polar
if all same and dipoles dont cancel out molecule is polar

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27
Q

dipole dipole forces

A

when attractive force bwteeen oppoiste charges of molecules is dipole dipole forces
partial charges

28
Q

how does dipole get stronger

A

as charge difference increases

29
Q

when does hydrogen bonding occur

A

when hydrogen is covalently bonded to nitrogen, oxygen or fluorine

30
Q

drawing hydrogen bonds

A

partial charges
lone pairs
draw hydrogen to lone pairs from all water molecules or whatever molecules on a strraight line2 hydrogens to 0 lone pair

31
Q

hydrogen bonding in water

A

-large difference in electronegativuty between hydrogen and oxygen
-causes H to have strong positive and O to have strong negative
-strong positive attracts lone pair of O
-neighouring atoms attracted to positive partial charge

32
Q

temporary dipoles

A

movement of electrons of non polar molecules means electrons can move and no longer have dipole so dipole temporary

33
Q

induced dipole

A

both charges on molecule so molecule with dipole repels electrons on negative side and move across molecule so negative side becomes positive so attracted molecules

34
Q

van der waal forces

A

arise when movement of electrons in one molecule creates a temporary dipole
-this induced dipole in a nearby molecule
-results in the attraction between partial charges of nearby molecules

35
Q

what do all polar molecules have

A

dipole di[pole forces
van der waal forces

36
Q

van der waal force strength down a group

A

fluorine has less electrons than iodine so less likely of even dispersion of electrons as more
stronger charge difference

37
Q

comparing boiling and melting points

A

-what bond present
-strength of bonds

38
Q

why dont molecular liquids and gases conduct electricity

A

-when heated intermolecular forces weaken but covalent bonds dont break so electrons not free to move between molecules and carry charge

39
Q

why is ice less dense than water

A

-hydrogen bonds that hold water molecules move further away from each other to make structure called open lattice structure

40
Q

macromolecules

A

large molecules with covalent bonds

41
Q

lattice made up of macromolecules

A

called a marcomolecular or giant covalent lattice

42
Q

what a lattice made up of smaller molecules

A

molecular lattice

43
Q

forces between chain marcomolecules

A

between chains

44
Q

forces between sheet macromolecules

A

between sheets

45
Q

large macromolecules like diamond

A

covalent bonds
no intermolecular forces

46
Q

diamond

A

macromolecular lattice held together by covalent bonds

47
Q

graphite

A

marcomolecular lattice bonded to 3 carbons each and graphene sheets held together by weak van der waal forces

48
Q

allotropes

A

different structures that can form when atoms of that element bond together

49
Q

allotropes of carbon

A

diamond
coal
graphene
graphite
buckminsterfullerene
nanotubes

50
Q

how does graphite have 3 bonds carbon

A

p orbital line in sheet how pi overlap sigma bonds
-p overlap strong bonds
like double bonds but not
1 spare electron from p orbital is delocalized

51
Q

why does diamond not conduct electricity

A

all of diamonds outer electrons are in covalent bonds so no delocalised electrons

52
Q

why can graphite conduct electricity

A

has delocalized electrons so can move freely throughout each layer and carry a charge

53
Q

hardness comparison of graphite and diamond

A

diamond very hard - drills
graphite very soft- pencils

54
Q

melting points of diamond and graphite

A

very high for both

55
Q

why does graphite have such a high melting point

A

have to break covalent bonds as well as intermolecular forces

56
Q

representing diamond n

A

C (s)

57
Q

why are marcomolecukles represented using empiricla formila

A

number of atoms doesnt effect properties of macromolecule

58
Q

mettalic bonding

A

-metallic lattice
-made up of delocalized electrona and cations
-held together by electrostatic forces between cations and delocalized electrons
high melting points
low solubility
-conduct electricity when solid and liquid
malleable
-ductile

59
Q

ionic bonding

A

-ionic lattice
cations and anions
held together by electrostatic forces between cations and anions
high melting points
usually high solubility
consustc electricity when dissolved in water
-brittle

60
Q

molecular lattices covalent bonding

A

-fewer than 1000 atoms
-intermolecular forces
low melting points
varying solubility
never conducts electricity

61
Q

giant structures

A

metallic
ionic
macromoleciar structures

62
Q

what happens when ionic substances dissolve in water

A

ions in lattice separate and surrounded by sphere of water molecules
-ions surrounded by water molecules are hydrated ions

63
Q

ion dipole

A

when hydrated ions stick to water molecules

64
Q

water of crystalisation

A

water molecules woven into salt lattice

65
Q

representing water of crystalisation

A

other molecules inlattice with dot and number of water molecules present to show how many per other molecule in lattice and that water regularly in lattice

66
Q
A

physical chem (8 decks)

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