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OCR A level Chemistry > Bonding and structure- shape of molecules > Flashcards

Bonding and structure- shape of molecules Flashcards

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1
Q

What shape occurs when there are 2 bonding pairs and no lone pairs?

A

Linear

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2
Q

What is the bond angle in linear molecules?

A

180

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3
Q

Give an example of a substance with a linear shape

A

BeF2

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4
Q

What shape occurs when there are 3 bonding pairs and no lone pairs?

A

Trigonal planar

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5
Q

What shape occurs when there are 4 bonding pairs and no lone pairs?

A

Tetrahedral

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6
Q

What shape occurs when there are 3 bonding pairs and 1 lone pair?

A

Trigonal pyramid

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7
Q

What shape occurs when there are 2 bonding pairs and 2 lone pairs?

A

Bent/v-shape

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8
Q

What shape occurs when there are 5 bonding pairs and no lone pairs?

A

Trigonal bipyramid

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9
Q

What shape occurs when there are 6 bonding pairs and no lone pairs?

A

Octahedral

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10
Q

What is the bond angle in trigonal planar?

A

120

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11
Q

What is the bond angle in tetrahedral?

A

109.5

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12
Q

What is the bond angle in bent/v-shaped?

A

104.5

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13
Q

What is the bond angle in trigonal pyramid?

A

107

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14
Q

What is the bond angle in octahedral?

A

90

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15
Q

What is the bond angle in trigonal bipyramid?

A

90 and 120

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16
Q

Give an example of a molecule which has as octahedral shape?

A

SF6

17
Q

Give an example of a molecule which has a trigonal bipyramidal shape

A

PF5

18
Q

Give an example of a molecule which has a trigonal pyramid shape

A

NH3

19
Q

Give an example of a molecule which has a trigonal planar shape

A

BH3

20
Q

Relative to single bonds, how much do double bonds repel?

A

Equally

21
Q

What shape of bonding is present in Carbon dioxide?

A

Linear

22
Q

When representing an ion in 3D what must you remember to draw?

A

Square brackets around the structure and the charge in the top right corner outside the brackets

23
Q

Explain why NH3 has a different shape to BH3

A
  • BH3 does not have any lone pairs so has a bond angle of 120
  • NH3 has one lone pair
  • Lone pairs repel more the bonding pairs so the atoms are pushed into a trigonal pyramid shape
24
Q

What conditions are needed for a bond to be non-polar?

A
  • the bonding atoms to be the same

- the bonded atoms have the same or similar electronegativity

25
Q

What happens to the electron pair in a non-polar bond?

A

The bonded pair is shared equally between the bonded atoms

26
Q

What kind of dipole is present in a polar covalent bond?

A

A PERMANENT dipole

27
Q

What would you look for in a molecule to tell if it has a polar bond?

A

A delta charge
a difference in electronegativity values
the presence of N, O, F, or Cl

28
Q

In addition to having polar bonds, molecules with a dipole must have what other property?

A

Asymmetry in the arrangement of the atoms

29
Q

What are the 3 types of intermolecular forces?

A
  • London forces (temporary dipole-dipole interactions)
  • Permanent dipole-dipole interactions
  • Hydrogen bonds
30
Q

What is the order of relative strength of intermolecular forces from weakest to strongest?

A
  • London forces
  • Permanent dipole-dipole interactions
  • Hydrogen bonding
31
Q

What does hydrogen bonding occur between?

A

The lone pair of an electronegative element and a hydrogen atom attached to an electronegative atom

32
Q

What is the shape around the hydrogen atom involved in the hydrogen bond?

A

linear

33
Q

What are the 3 anomalous properties of water?

A

1) High melting and boiling point compared to similar molecules
2) Expansion on freezing (The solid is less dense than the liquid)
3) High surface tension

34
Q

How many hydrogen bonds can a water molecule form?

A

4

35
Q

Why can a water molecule form 4 hydrogen bonds?

A
  • it has 2 lone pairs on the oxygen

- it has 2 hydrogen atoms

36
Q

Why does ice float on water?

A
  • Hydrogen bonds in ice hold water molecules apart in an open lattice structure
  • Water molecules in ice are further apart than in water
  • Solid ice is less dense than liquid water and floats

OCR A level Chemistry (30 decks)

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