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Wjec Chemistry Unit 1 > 1.5 > Flashcards

1.5 Flashcards

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1
Q

Crystal co-ordination number of Caesium chloride

A

8:8

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2
Q

Crystal co-ordination number of Sodium chloride

A

6:6

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3
Q

Why is CsCl co-ordination number bigger than NaCl

A

Cs+ is a larger ion so it can accommodate more Cl anions

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4
Q

How are ionic crystal structures arranged

A

Ions are arranged so that the electrostatic attraction between oppositely charged ions is greater than electrostatic repulsion between ions of the same charge

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5
Q

Describe the shape of sodium chloride

A

Cubic lattice

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6
Q

Look

A
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7
Q

Caesium chloride shape

A

Lattice made up of 2 interpenetrating simple cubic structures

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8
Q

Look

A
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9
Q

Which ion to show as smaller in diagrams of ionic crystal structures

A

The cation

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10
Q

Physical properties of ionic crystal structures

A
  • high melting temperature
  • soluble in water
  • hard but brittle
  • conducts electricity when liquid but not solid
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11
Q

High melting temperature of NaCl

A

Giant lattices held by strong electrostatic forces between oppositely charged ions which require a lot of energy to overcome

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12
Q

Solubility in water of NaCl

A

As water molecules are polar when in solution the O&- attracted to the cations and the H&+ to the anions
The water molecules pull the ions away form the lattice and the solid dissolves

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13
Q

Hard but brittle property of NaCl

A

When force is applied the layers of ions slide over each other which causes the ions of the same charge to be next to each other which causes the ions to repel each other and the crystal shatters

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14
Q

Describe electrical conductivity of NaCl

A

Solid - poor as the ions are fixed in position by ionic bonds
Liquid - good are the ions are no longer in a lattice and so can move freely and carry a flow of charge = electrical current

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15
Q

Describe the structure and bonding in diamond

A

• tetrahedral structure due to each C atom covalently bonded to 4 others

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16
Q

Diamond properties

A
  • high melting temperature
  • doesn’t conduct electricity
  • very hard
  • insoluble in water
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17
Q

Look

A
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18
Q

Why does diamond have a very high melting temperature

A

Strong covalent bonds between atoms

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19
Q

Why doesn’t diamond conduct electricity

A

No free electrons to carry an electrical current

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20
Q

Why is diamond so hard

A

Strong C-C bonds and due to its geometrical rigidity

21
Q

Why is diamond insoluble in water

A

No ions present to be attracted by polar water molecules

22
Q

Describe structure and bonding in graphite

A
  • layers of hexagonal rings held by van der waals forces
  • within the layers each C is covalently bonded to 3 others
  • 4th electron from each C atom is delocalised within the layer
23
Q

Look

A
24
Q

Properties of graphite

A
  • high melting temperature
  • good electricity conductor
  • insoluble in water
  • soft, slippery feel
  • low density
25
Q

Why does graphite have a high melting temperature

A

There are strong covalent bonds in hexagonal layers

26
Q

Why is graphite a good electricity conductor

A

Delocalised electron is free to move along the layers so an electrical current can flow
Only conducts parallel to it’s lines as the electron isn’t free to move from one layer to the next

27
Q

Why is graphite insoluble in water

A

No ions to attract polar water molecules

28
Q

Why does graphite have a soft, slippery feel?

A

The Van der waals forces between layers are easily broken so the layers can slide over each other
May be used as lubricant

29
Q

Why does graphite have a low density

A

There is a lot of space between layers as the length of the van der waals are longer than the covalent bonded
May be used as strong, lightweight sport equipment

30
Q

Structure of iodine

A

Crystal lattice

Covalent bonds within molecules held together by van der waals forces

31
Q

Properties of iodine

A
  • low melting temperature
  • poor electrical conductors
  • normally insoluble in water
32
Q

Look

A
33
Q

Why does Iodine have a low melting temperature

A

Weak van der waals forces between molecules which don’t need much energy to break

34
Q

Why is Iodine a poor electrical conductor

A

Doesn’t contain charged particles

35
Q

Why are molecules such as iodine normally insoluble in water

A

No ions to attract the polar water molecules

36
Q

Describe the structure of ice

A
  • water molecules are arranged in rings of 6 held by hydrogen bonds
  • each water molecule is hydrogen bonded to 4 others in a tetrahedral coordinated lattice structure
  • water molecules spread out and it has an open structure and so a lower density than water
37
Q

Properties of ice

A
  • unusually high boiling point

* poor conductors of electricity

38
Q

Why does ice have an unusually high boiling point

A

Due to presence of hydrogen bonds

39
Q

Why is ice a poor conductor of electricity

A

Doesn’t contain delocalised electrons or ions

40
Q

Look

A
41
Q

Describe the structure and bonding of metals

A
  • giant metallic structure
  • regular arrangement of metal cations (lattice) which is surrounded by a sea of delocalised electrons
  • strong metallic bond due to electrostatic forces of attraction between nucleus of cations and delocalised electrons
  • increasing temperature with increased number of delocalised electrons as the attraction is higher - more electrons and stronger cation
42
Q

Properties of metals

A
  • high melting temperature
  • hard
  • good thermal conductor
  • good electrical conductors
  • malleable and ductile
43
Q

Why do metals have high melting temperatures

A

Strong forces of attraction

44
Q

Why are metals hard

A

Strong metallic bonds

45
Q

Why are metals good thermal conductors

A

Delocalised electrons can pass kinetic energy to each other

46
Q

How are metals good conductors of electricity

A

Delocalised electrons carry current as when a potential difference is applied across end of a metal
Electrons will be attracted and move towards the positive terminal of the cell

47
Q

Why are metals malleable and ductile

A

When force is applied the layers of cations can slide over each other but as the delocalised electrons move with the cations it prevents the forces of repulsion forming between layers

48
Q

Look

A

Wjec Chemistry Unit 1 (9 decks)

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