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Chemistry OCR A-Level > Chapter 6 > Flashcards

Chapter 6 Flashcards

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1
Q

What is the electron-pair repulsion theory?

A

1) electron pairs repel so they are arranges as far as possible
2) arrangement of electron pairs minimises repulsion and holds bonded atoms in shape

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2
Q

Is a lone pair of electrons closer or further to the central atom, than a bonded pair?

A

closer

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3
Q

Does a lone pair of electrons repel more strongly or less strongly than a bonded pair?

A

more

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4
Q

What is the relative repulsions between lone pairs and bonding pairs?

A

bonded-pair/bonded-pair < bonded-pair/bonded-pair < lone-pair/lone-pair

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5
Q

What is the name of the shape with 4 bonded pairs and 0 lone pairs?

A

tetrahedral

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6
Q

What is the name of the shape with 3 bonded pairs and 1 lone pair?

A

pyramidal

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7
Q

What is the name of the shape with 2 bonded pairs and 2 lone pairs?

A

non-linear

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8
Q

What is the bond angle of 4 bonded pairs and 0 lone pairs?

A

109.5

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9
Q

What is the bond angle of 3 bonded pairs and 1 lone pairs?

A

107

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10
Q

What is the bond angle of 2 bonded pairs and 2 lone pairs?

A

104.5

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11
Q

What is the name of the shape with 3 bonded pairs and 0 lone pairs?

A

trigonal planar

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12
Q

What is the bond angle with 3 bonded pairs and 0 lone pairs?

A

120

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13
Q

What is the name of the shape with 2 bonded pairs and 0 lone pairs?

A

linear

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14
Q

What is the bond angle with 2 bonded pairs and 0 lone pairs?

A

180

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15
Q

What is the name of the shape with 6 bonded pairs and 0 lone pairs?

A

octahedral

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16
Q

What is the bond angle with 6 bonded pairs and 0 lone pairs?

A

90

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17
Q

Why does electronegativity change when the bonded atoms are different elements?

A

1) nuclear charges are different
2) atoms may be different sizes
3) shared pair of electrons may be close to one nucleus

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18
Q

What is electronegativity?

A

the attraction of a bonded atom for the pair of electrons in a covalent bond

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19
Q

Does nuclear charge increase or decrease across the periodic table?

A

increase

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20
Q

Does atomic radius increase or decrease across the periodic table?

A

increase

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21
Q

Does electronegativity increase or decrease across the periodic table?

A

increase

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22
Q

Does electronegativity increase or decrease up the periodic table?

A

increase

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23
Q

If the electronegativity difference is 0, what is the bond type?

A

covalent

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24
Q

If the electronegativity difference is 0-1.8, what is the bond type?

A

polar covalent

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25
Q

If the electronegativity difference is >1.8, what is the bond type?

A

ionic

26
Q

When is a bond non-polar?

A

1) bonded atoms are the same
OR
2) bonded atoms have same/similar electronegativity

27
Q

Do non-polar solvents mix with water?

A

no

28
Q

What is the separation of opposite charges?

A

dipole

29
Q

What is a permanent dipole?

A

a dipole in a polar covalent bond

30
Q

Why is a carbon dioxide, CO₂, molecule non-polar?

A

1) C=O bonds have a permanent dipole
2) dipoles act in opposite directions
3) dipoles cancel and overall dipole is 0

31
Q

What are intermolecular forces?

A

weak interactions between dipoles of different molecules

32
Q

What are the types of intermolecular forces?

A

1) induced dipole-dipole interactions (London forces)
2) permanent dipole-dipole interactions
3) hydrogen bonding

33
Q

Are London forces strong or weak?

A

weak

34
Q

Do London forces exist between all or some molecules?

A

all

35
Q

What do London forces act between?

A

induced dipoles

36
Q

What is the origin of induced dipoles?

A

1) instantaneous dipole exists at any instant
2) instantaneous dipole induces dipole on neighbouring molecule
3) induced dipole induces further dipoles on neighbouring molecules

37
Q

Are induced dipoles permanent or temporary?

A

temporary

38
Q

The more electrons in a molecule, the … the instantaneous and induced dipoles.

A

larger

39
Q

The more electrons in a molecule, the … the induced dipole-dipole interactions.

A

greater

40
Q

The more electrons in a molecule, the … the attractive forces between molecules.

A

stronger

41
Q

What do permanent dipole-dipole interactions act between?

A

permanent dipoles in polar molecules

42
Q

What are the molecule in a simple molecular lattice held in place by?

A

weak intermolecular forces

43
Q

How are the atoms within each molecule of a simple molecular lattice bonded?

A

strongly by covalent bonds

44
Q

How can the weak intermolecular forces in a simple molecular lattice be broken?

A

by the energy present at low temperatures

45
Q

Do simple molecular substances have low or high melting and boiling points?

A

low

46
Q

When a simple molecular lattice is melted, what breaks?

A

only weak intermolecular forces

47
Q

Are simple molecular substances soluble or insoluble in non-polar solvents?

A

soluble

48
Q

Are simple molecular substances soluble or insoluble in polar solvents?

A

insoluble

49
Q

Why are simple molecular substances insoluble in polar solvents?

A

1) little interaction between molecules in lattice and solvent molecules
2) intermolecular bonding in polar solvent too strong to be broken

50
Q

Why can polar covalent substances dissolve in polar solvents?

A

polar solute molecules and polar solvent molecules attract each other

51
Q

Are simple molecular structures conductors or non-conductors of electricity?

A

non-conductors

52
Q

Why are simple molecular structures non-conductors of electricity?

A

1) no mobile charged particles

2) can’t complete an electrical circuit

53
Q

What is a hydrogen bond?

A

1) special type of permanent dipole-dipole interaction

54
Q

Hydrogen bonds are found in molecules containing what?

A

1) electronegative atom with lone pair of electrons

2) H-atom attached to electronegative atom

55
Q

What are the electronegative atoms with a lone pair of electrons that undergo hydrogen bonding?

A

1) nitrogen
2) oxygen
3) fluorine

56
Q

What are the strongest type of intermolecular attractions?

A

hydrogen bonds

57
Q

How is a hydrogen bond shown?

A

dashed line

58
Q

Is ice more or less dense than water?

A

less

59
Q

Why is solid ice less dense than liquid water?

A

1) hydrogen bonds hold water molecules apart in open lattice structure
2) water molecules in ice further apart than water
3) solid ice less dense than liquid water + floats

60
Q

Does water have a high or low melting and boiling point?

A

high

61
Q

Why does water have a high melting and boiling point?

A

1) hydrogen bonds are extra forces, over London forces

2) large quantity of energy needed to break hydrogen bonds in water

Chemistry OCR A-Level (28 decks)

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