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a level chemistry > module 2 section 2 - electrons, bonding and structure > Flashcards

module 2 section 2 - electrons, bonding and structure Flashcards

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1
Q

state the properties of ionic compounds (4)

A
  • giant ionic lattice
  • solid at RTP
  • soluble
  • conduct electricity when molten but not when solid
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2
Q

explain why ionic compounds are solid at RTP (3)

A
  • strong attraction between ions
  • lots of energy needed to overcome attraction
  • to break bonds
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3
Q

explain the solubility of ionic compounds (3)

A
  • dissolve in polar solvent
  • cations attracted to oxygen
  • anions attracted to hydrogen
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4
Q

describe and explain the electrical conductivty of ionic compounds (4)

A
  • dont conduct when solid
  • as ions fixed in place in lattice structure
  • conduct when molten
  • ions are mobile
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5
Q

describe what is meant by the term ionic lattice in terms of the type and arracngement of particles present (2)

A
  • repeating pattern
  • of oppositely charged ions
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6
Q

what direction do oppositely charged ions attract ?

A

in all directions

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7
Q

give an example of a hypovalent compound

A

BF3

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8
Q

give an example of a hypervalent molecule

A

SF6

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9
Q

what is hypovelent

A

when one atome is covalently bonded but hasnt got a full outer shell

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10
Q

what is hypervalent

A

when one atom covalently bonded has more than 8 electrons in its outer shell

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11
Q

h

A

j

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12
Q

O-O = +300KJmol-1
O=O = +500KJmol-1

why are these values positive and what does this tell you about the strength of the O=O compared to O-O ? (3)

A
  • positive because energy has to be put in to break bond
  • = endothermic process
  • O=O bond is stronger than O-O
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13
Q

Draw the structure of a linear bond

A
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14
Q

Draw the structure of a trigonal planar bond

A
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15
Q

Draw the structure of a tetrahedral bond

A
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16
Q

Draw the structure of a (trigonal) pyramidal bond

A
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17
Q

Draw the structure of a non linear bond

A
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18
Q

Draw the structure of an octahedral bond

A
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19
Q

State the shape and bond angle of a bond that has 2 electron regions 2 bonding regions and 0 lone pairs (2)

A
  • linear
  • 180
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20
Q

State the shape and bond angle of the bind that has 3 electron regions 3 bonding regions 0 lone pairs (2)

A
  • trigonal planar
  • 120
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21
Q

State the shape and bond angle of a bond that has 4 electron regions 4 bonding regions and 0 lone pairs

A
  • tetrahedral
  • 109.5
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22
Q

State the shape and bond angle of a bond that has 4 electron regions 3 bonding regions and 1 lone pair (2)

A
  • pyramidal
  • 107
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23
Q

State the shape and bond angle of a bond that has 4 electron regions, 2 bonding regions and 2 lone pairs (2)

A
  • non linear
  • 104.5
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24
Q

State the shape and bond angle of a bond that has 6 electron regions 6 bonding regions and 0 lone pairs (2)

A
  • octahedral
  • 90
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25
Q

What is meant by a bond? (1)

A

A region of electron density

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26
Q

How do lone pairs of electrons compare to bonded pairs? (1)

A

A region of much greater electron density

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27
Q

What makes a molecules more stable (3)

A
  • Greater bond angle
  • less repulsion
  • more stable
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28
Q

Ammonia and boron trifluoride both have 3 bonding regions. Why is ammonia not also a tribunal planar?

A

Ammonia has a lone pair of electrons

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29
Q

Ammonia and methane both have 4 electron regions why is ammonia not also tetrahedral

A

Lone pairs repel more than bonded pairs

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30
Q

Why is water not linear? (2)

A

Bonded pair - bonded pair
Lowest energy arrangement

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31
Q

Explain the difference on how bonded and lone pairs repel

A

• Bonded pairs repel eachother equally
- lone pairs repel more than bonded pairs
- Each lone pair reduces the bond angle between bonded pairs by 2.5°

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32
Q

Explain the bond angle in sulfur hexafluoride (3)

A

• 90° bond angle
. 6 bonding regions and no lone pairs
• bonded pairs repel eachother equally

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33
Q

Explain the bond angle in phosphorous trichloride (3)

A
  • 107° bond angle
    • 3 bonding regions and I I one pair
  • lone pairs repel more than bonded pairs
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34
Q

Explain the bond angle in water (3)

A

• 104.5 bond angle
• 2 bonding regions and 2 lone pairs
. Lone pairs repel more than bonded pairs

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35
Q

Explain the bond angle in a sulfate lon(3)

A
  • 109.5° bond angle
    • 4 bonding regions
    • bonded pairs repel eachother equally
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36
Q

Predict the shape of this ion (5)

A

• 4 electron regions
• 3 bonding regions
- 1 lone pair
• 107° band angle
•Pyramidal

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37
Q

How do lone pairs of electrons compare to bonded pairs (1)

A
  • a region of much greater electron density
38
Q

Predict the shape of this ion (5)

A

• 3 electron regions
• 3 bonding regions
• o lone pairs
• 120° band angle
• trigon al planar

39
Q

Predict the shape of this molecule (5)

A
  • 7 electron regions
  • 3 bonding regions
  • 2 lone pairs
  • 104.5° bond angle
  • non linear
40
Q

Predict the shape of this molecule (5)

A
  • 2 electron regions
  • 2 bonding regions
  • o lone pairs
  • 180° bond angle
    -Linear
41
Q

The shape around the oxygen atom in butan-2 -ol is non-linear, predict the c-o-h bond angle and explain this shape (4)

A

• 104.5° band angle
• it has 2 banded pairs and 2 lone pairs
• lone pairs repel more than bonded pairs

42
Q

Explain now a covalent bond can be polar (3)

A

• when 2 atoms in a covalent bond have different
Electronegativities
• electron distribution is asymmetrical
• giving atoms partial charges

43
Q

Which direction does a dipole moment point

A

+ to -

44
Q

What does magnitude of a dipole moment show

A

How polar the bond is

45
Q

How do polar bonds occur (3)

A

• Asymmetry in a bond
- 1 atom more electronegative
• electron cloud distribution =unsymmetrical

46
Q

1s NH3 a polar molecule (2)

A
47
Q

Explain why CCI4 has polar bonds (1)

A

Cl atom is more electronegative than C atom

48
Q

Explain why Cecil is not a polar molecule (2)

A

• Does not have an overall dipole
• dipoles act in opposite directions so cancel out (symmetry)

49
Q

Show wether or not SF6 is polar (3)

A

• Octahedral + symmetrical
• au dipoles act in = and opposite directions
• non polar molecule with polar bonds

50
Q

Show if H2O is polar or not (3)

A

• non linear + asymmetric
• dipoles both point up-same direction
Polar molecule

51
Q

Show if PCI3 is a polar molecule or not (3)

A

• Pyramidal and asymmetrical
• dipoles all point is same direction
O polar molecule

52
Q

Show If NH4+ is polar or not (3)

A

-Tetrahedral and symmetrical
- point in opposite directions S cancel out
- non polar molecule with polar bonds

53
Q

Show if CO3 2- is polar ion or not (3)

A

• Dipoles point in opposit directions so cancel out
• tribunal planar and symmetric
• non polar with polar bonds

54
Q

Show is CH2O is a polar molecule or not

A

Trigonal planar and asymmetrical
Dipoles all face up = same direction
Polar molecule

55
Q

Show if BCl2F is a polar molecule or not (3)

A

• Trig planar and asymmetrical
. B-f dipole is more electronegative than B-CI dipole
• overall dipoles act in 1 direction as B-CI don’t cancel out b-f dipole

56
Q

Explain if NCl3 is a polar molecule or not (3)

A

• Asymmetrical and pyramidal
point in same direction
• polar

57
Q

Explain why iodine has a higher melting point than fluorine (2)

A

• More electrons
• stronger London forces between molecules

58
Q

explain how induced dipole dipole interactions arise (3)

A
  • random movement of electrons
  • induces a dipole in another molecule
  • attraction between delta + and delta - BETWEEN molecules
59
Q

what factors increase the strength of induced dipole dipole interactions (2)

A
  • increased number of electrons in molecule
  • increased points of contact / SA
60
Q

explain how an increased number of electrons in a molecule leads to a higher MP and BP (5)

A
  • larger molecule = increased electrons
  • larger difference in temporary dipole
  • = stronger IDDI between molecule
  • = more energy needed to overcome IDDI
  • = greater MP + BP
61
Q

explain how increased points of contact increase the MP and BP of a molecule (5)

A
  • straight chain molecules
  • molecules can get closer together
  • stronger IDI between molecules
  • more energy needed to overcome
  • = greater MP + BP
62
Q

describe the properties of molecule which have IDDI forces regarding MP and BP (3)

A
  • stronger IDDI forced BETWEEN molecules
  • more energy needed to overcome force and separate mlcls
  • greater MP + BP
63
Q

describe the properties of molecule which have IDDI forces regarding solubility (2)

A
  • like dissolves like
  • molecules with similar intermolecular forces attract
64
Q

what can induced dipole dipole interactions also be called (2)

A
  • instantaneous dipole induced-dipole forces
  • London dispersion forces
65
Q

why is the attraction between IDDI so weak (3)

A
  • areas of electro positivity attracts areas of electronegativity
  • dipole in only temporary
  • so when there is no diff in electron density there is no attraction
66
Q

why is attraction in PDDI stronger than in IDDI (2)

A
  • dipole is permanent
  • attraction remains constant
67
Q

explain how permanent dipole dipole interactions arise (3)

A
  • polar mlcls
  • [permanent dipoles
  • attraction between delta + and delta - BETWEEN molecules
68
Q

what factors increase the strength of PDDI (3)

A
  • larger diff in electronegativity
  • increased number of electrons in molecule
  • increased points of contact / SA
69
Q

explain how difference in electronegativity affects strength of PDDI (3)

A
  • larger diff in electronegativity
  • = larger diff in dipole
  • = stronger PDDI between molecules
70
Q

are molecules which contain IDDI as their strongest attraction soluble in water or not. explain your answer (2)

A
  • no (insoluble)
  • because they are non polar mlcls
71
Q

is c3h6o soluble in water? justify your answer (3)

A
  • soluble
  • sort chained polar molecule
  • contains less than carbon atoms
72
Q

is C4H8O soluble in water? justify your answer (3)

A
  • not soluble
  • long non polar chain
  • so wont dissolve
73
Q

what is the strongest intermolecular force ?

A

H-bonds

74
Q

what is the weakest intermolecular force ?

A

IDD forces

75
Q

state the anomalous properties of hydrogen bonds (2)

A
  • lower density of ice compared to water
  • relatively high MP + BP
76
Q

explain why ice is less dense that liquid water (3)

A
  • water can form 4 Hbonds w neighboring mlcls
  • mlcls held further apart by Hbonds
  • gives ice a tetrahedral structure
77
Q

describe the the MP+BP of molecules containing hydrogen bonds are relatively high (2)

A
  • H bonding = strongest intermlclr force
  • need for energy to overcome
78
Q

NH3 = -33 degrees BP
PH3 = -88 degrees BP
ASH3 = -55 degrees BP
SbH3 = -17 degrees BP

explain the trends in boiling points (4)

A
  • PH3, AsH3 and SbH3 have IDDI only
  • so BP increases as no. e- in mlcl increases
  • NH3 has H bonding
  • H bonding is stronger than IDDI so more energy to overcome
79
Q

why is the solubility of chloroform (CHCl3) 10 times greater than that of carbon tetrachloride (CCl4) in water ? (3)

A
  • C-H bond in chloroform is more polarised due to increased electronegativity of Cl atoms
  • CHCl3 = polar mlcl but CCl4 = tetrahedral so no overall dipole moment
  • polar water mlcls interact better w polar CHCl3 mlcls then non polar CCl4 mlcls
80
Q

explain why BP of water is higher than both HF and NH3 (3)

A
  • each H2O mlcl can form 4 H bonds
  • higher BP than NH3 as H bonds are stronger and has more polar bonds and conatin 2X as many H bonds
  • higher BP than HF as has 2X as many Hbonds
81
Q

what is the formula for ethanol ?

A

CH4OH

82
Q

Describe trend shown in graph for H2S, H2Te, and HCl (1)

A

As size of mock increases Bp increases

83
Q

Compare and contrast boiling points of H2S and HCl (2)

A
  • both have PDDI
  • but H2S has higher BP as it’s a larger mlcl
84
Q

Boiling points in data shows 2 anomalies, explain why they are anomalous and suggest reasons for these (2)

A
  • HF and H2O are much smaller mocks but have higher BP’s
  • as they have Hbonds which are stronger intermolecular forces
85
Q

Which molecules can form hydrogen bonds with another molecule of itself (7)

A

-NH3
-C2H6O
-HF
-NH2, O2,H2N,OH

86
Q

Which of these molecules can form hydrogen bonds with a water molecule (7)

A
  • all of them
87
Q

Can this molecule form. Hydrogen bind with itself and with a water molecules

A
  • itself: yes
    -water - yes
88
Q

Can this molecule form a hydrogen bind with itself and with water

A

Itself: yes
Water: yes

89
Q

Can this molecule for a hydrogen bind with itself and with water

A

Itself : no
Water: yes

90
Q

Can this molecule form a hydrogen bond with itself and with water ?

A

Itself : no
Water: no (no lone pair on N atom)

a level chemistry (9 decks)

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