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CHEMISTRY > Key concepts.2 > Flashcards

Key concepts.2 Flashcards

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1
Q

Bonding with ionic compounds

A

Ionic bonds are strong electrostatic forces of attraction between oppositely charged ions

Eg sodium reacts with chlorine = NaCl
•electrons transfer from sodium atoms to chlorine atoms
• Na+ ions and Cl- ions form
• Na+ and Cl- ions attract each other

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2
Q

Structure of ionic compounds

A

The ions in an ionic compound form a lattice structure which has :
• a regular arrangement of ions
• ionic bonds between oppositely charged ions

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3
Q

Properties of ionic compounds

A

Usually have high melting point
Hugh boiling point

Solid state at room temperatures

Many strong ionic bonds
Large amounts of energy must be transferred to the lattice structure to break these bonds

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4
Q

Ionic compounds solubility in water

A

Ionic compounds are often soluble in water. They dissolve to form aqueous solutions

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5
Q

What structure is an ionic compound

A

A lattice

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6
Q

State why sodium chloride does not conduct electricity when it is in the solid state

A

The ions are not free to move around in a solid

Although ions are electrically charged, they are held in fixed positions in the lattice structure

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7
Q

Explain why sodium chloride does not conduct electricity when it is molten or in aqueous solution

A

The ions are free to move around when sodium chloride is liquid or when it is dissolved in water. This means they can carry electric charge from place to place

An electric current is a flow of charge. A substance will conduct electricity if :
• it contains charge carriers (such as ions)

These charge carriers are free to move through the substance

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8
Q

How is a covalent bond formed

A

When a park of electrons is shared between two atoms

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9
Q

Properties of covalent bonds

A
  • are strong
  • form between non-metal atoms
  • often produce molecules, which can be elements or compounds

A hydrogen atom can form one covalent bond. Usually for atoms of other non-metals :
•number of bonds = (8-group number)

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10
Q

Helium and other elements in group 0 have full outer shells therefore they do not transfer or share electrons so they are

A

Unreactive

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11
Q

What are three ways you can represent a covalent bond

A

Dot and cross with shells

Dot and cross without shells

Structural formula

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12
Q

Typical size of atoms

A

1 x 10^-10

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13
Q

Size of simple molecules

A

1 x 10^-9

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14
Q

What does a simple molecule consist of

A

Just a few atoms, joined to each other by strong covalent bonds. Simple molecular substance can be :

Non metal elements such as H2 O2 Cl2

Compounds of non-metals such as HCl H2O CH4

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15
Q

Properties of simple molecular substances ususallaee are:

A

Low melting points
Low boiling points

Usually has or liquid at room temperature

Simple molecular substances with relatively large molecules such as wax are in the solid state at room temperature

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16
Q

There are weak attractive forces between molecules called?

A

Intermolecular forces

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17
Q

When a simple molecular substance such as oxygen melts or boils :

A

Intermolecular forces are overcome

Covalent bonds do not break

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18
Q

Simple molecular substances do not conduct electricity when

A

Solid liquid gas because
Molecules are not electrically charged and
Do not contain electrons that are free to move forward

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19
Q

What are simple molecular s solubility

A

Many simple molecular substances are insoluble in water. The intermolecular forces between water and these substances are weaker than those between:
•water molecules
• molecules of the substance itself

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20
Q

Simple molecular substance dissolve in water if they can from strong enough intermolecular forces with water molecules :

A

Hydrogen and oxygen are sparingly soluble (very little dissolves)
Chlorine, carbon dioxide, sulfur dioxide and ammonia are soluble in water
Ethanol and ethanol acid are soluble
Sugar is soluble in water

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21
Q

Nitrogen is a colourless, unreactive has at room temperature
Explain why it is suitable for use as an insulator in high-voltage electrical transformers

A

Nitrogen is unreactive.
Will not react with materials used in transformer
Can insulate parts in transformer because it doesn’t conduct electricity

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22
Q

Giant molecular substances contain

A

Very many atoms rather than just a few

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23
Q

In a giant molecules the atoms are :

A

Joined by strong covalent bonds

Arranged in a regular lattice structure

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24
Q

Giant molecular substances can be :

A
  • non-metal elements such as carbon

* compounds such as silica

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25
Q

Giant molecular substances usually have :

A

Hugh melting points

Hugh boiling points

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26
Q

What state are giant molecular substances at room temperature

A

Solid.
A lot of energy must be transferred to break the many strong covalent bonds during meetings and boiling
Insoluble in water

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27
Q

What are diamond and graphite both forms of?

A

Carbon.

Giant molecular substances

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28
Q

Diamond

A

Each atom is bonded to four others

Strong covalent bonds between atoms

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29
Q

Graphite

A

Each atom is bonded to three others

Weak intermolecular forces between layers

Strong covalent bonds between atoms in a layer

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30
Q

Explain why graphite conducts electricity whereas diamond does not

A

Carbon atom can form four covalent bonds. In graphite each carbon atom only forms three covalent bonds, the non-bonding outer electrons become delocalised. This means that they can move through the structure so graphite conducts electricity. Diamond does not have delocalised and so does not conduct

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31
Q

Diamond has a rigid lattice structures and strong bonds which make it very

A

Hard this is why it is useful for cutting tools

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32
Q

In graphic the weak intermolecular forces let the layers slide over each other :

A

This is why it is slippery and useful as a lubricant

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33
Q

Metals have delocalised electrons which makes them

A

Good conductors if electricity

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34
Q

Graphemes and fullerenes are forms of

A

Carbon

Giant molecules

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35
Q

What is graphene

A

A giant molecular substance
Structure of resembles a single layer of graphite

Each carbon atom is covalently bonded to 3 other carbon atoms
It has a regular lattice structure
Interlocking hexagonal rings of carbon atoms

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36
Q

Graphene conducts electricity:

A

The non-bonding outer electrons become Delocalised

They can move through the structure

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37
Q

Graphene is very strong and flexible

A

It contains many strong covalent bonds

38
Q

Grapheme is almost transparent

A

It’s layers are just one atom thick

39
Q

What’s fullerenes

A

They resemble a sheet of graphene rolled to form either :

  • hollow balls = buckyballs
  • hollow tubes = nanotubes
40
Q

What is it called when the grapheme is the road to form hollow balls

A

Fullerenes called buckyballs

41
Q

What is it called when graphene is rolled to form hollow tubes

A

Fullerenes, nanotubes

42
Q

Buckminsterfullerene formula

A

C60

43
Q

C60 has

A

Carbon atoms arranged in pentagons as well as hexagons

Buckminterfullerene

44
Q

Materials made from buckyballs:

A

Conduct electricity because I have delocalised electrons

A soft one in the solid-state because they have weak intermolecular forces

45
Q

What is at nanotubes ends

A

They’re closed ends or open ends

46
Q

How long can nanotubes be

A

Several millimetres long

47
Q

Properties of nanotubes

A

Conduct electricity because they have delocalised electrons

Very strong because the structure has many strong covalent bonds

48
Q

What are polymers

A

Large molecules made from many small molecules called monomers joined together

49
Q

What a polymer molecules described as rather than giant covalent molecules

A

Macromolecules

50
Q

Polly(Ethene) is not a fullerene:

A

It is a hydrocarbon (compound of hydrogen and carbon)

51
Q

Most elements are……. and placed in the…….. side of the periodic table

A

Metals

Left

52
Q

Appearance of metals and non-metals

A

Metals are shiny

Non-metals are dull

53
Q

Electrical property of metals and non-metals

A

Metals - good

Non-metals - poor

54
Q

Conduction of metals and non-metals

A

Both Conductors

55
Q

Density of metals + non-metals

A

Density of metals is High

Density of non metals is low

56
Q

Melting point of non metals and metals

A

Melting point of metals is high

Melting point of non metals is low

57
Q

Mercury’s is a ……….. at room

A

Liquid

58
Q

Diamond and graphite have a very high melting point even though there non metals

A

Graphit condycts electricitt

59
Q

Metals are

A

Malleable - can be pressed into shape without shattering

60
Q

Non metals are

A

Brittle

In the solid state they shatter when bent or hit

61
Q

Metallic structure and bonding

A metal:

A

Consists of a giant lattice of positively charged metal ions

Has a ‘sea’ of delocalised electrons

The delocalised electrons come from the outer shells of the atoms

Metallic bonds are strong electrostatic forces between positive metal ions and delocalised electrons

62
Q

Malleable metals

Is a force is applied to a metal:

A

Layers of positive ions slide over each other

The metal changes shape without shattering

63
Q

Insoluble metals :

A

Metals are insoluble in water, however some metals do seem to dissolve in water

This is because they react with the water to produce soluble metal hydroxides

This dissolve, exposing more metal to the water

Eg sodium reacts with water forming sodium hydroxide solution and hydrogen :

2Na (s) + 2H2O (l) -> 2NaOH (aq) + H2 (g)

64
Q

Explain why metals are good conductors of electricity

A

Metals contain delocalised electrons which can move through the structure of the metal

65
Q

What does ductile mean

A

Can be pulled to make wires without breaking .
The layers of positive ions slide over each other

Eg copper

66
Q

Mercury is a liquid metal at room temperature, state wether it should conduct electricity with a reason

A

It should because it will have delocalised electrons

67
Q

The formula for a substance can be written as :

A

A structural formula
A molecular formula
An empirical formula

68
Q

What does the empirical formula show

A

The simplest whole number ratio of atoms of each element. This does not show how the atoms are arranged or (usually) the actual number of atoms

CH2O

69
Q

What’s the molecular formula

A

The number of atoms of each element
This does not show how the atoms are arranged

C2H4O2

70
Q

What does the structural formula show

A

The number of atoms of each element. This gives us an idea of how they are arranged

CH3COOH

71
Q

When you draw a structure you should show all the covalent bonds in the molecule

Some models may not show

A

The molecules three- dimensional shape

The bonding and non-bonding electrons

72
Q

You can draw ball-and-stick models.

A

Also make them using plastic modelling kits

73
Q

What do ball-and-stick models show

A

How each atom is bonded to other atoms

The molecules three-dimensional shape

74
Q

What do ball-and-stick models not show

A

The bonding and non-bonding electrons

Or each elements chemical symbol

75
Q

What’s another model which is similar to ball-and-stick but more accurate?

A

Space-filling models

76
Q

Positive and negative of space-filling models

A

The sizes of atoms are relative to their bonds

You may not be able to see all the atoms in a complex space-filling model

77
Q

Positive and negatives of dot and cross diagrams

A

Shows symbol for each atom in molecule
Shows how each atom is bonded to other atoms
Non-bonding pairs of electrons in the outer shells are included
Pairs of electrons in each covalent bond are shown by dots and crosses

Doesn’t show three dimensional shape

78
Q

State a limitation of empirical formula

A

Empirical formula does not show
Actual number of atoms\how the atoms are arranged/three-dimensional shapes of molecules/bonding and non-bonding electrons/sizes of atoms relative to the bonds

79
Q

Limitation of molecular formula

A

Does not show How the atoms are bonded/three-dimensional shape of molecule/bonding a number ending electrons/size of atoms relative to their bonds

80
Q

Limitations of structural formula

A

Does not show: three-dimensional shape of molecule/bonding and non-bonding electrons/sizes of atoms relative to the bonds

81
Q

Limitations of drawn formula

A

Does not show: three-dimensional shape of molecule/bonding and non-bonding electrons/sizes of atoms relative to their bonds

82
Q

Limitations of ball and stick model

A

Does not show: element symbols/Bonding a non-bonding electrons/sizes of atoms relative to the bonds

83
Q

Limitations of space – filling model does not show

A

Element symbols/ bonding and non-bonding electrons/ some atoms in complex models

84
Q

Limitations of dot and cross diagram

A

Does not show:

Three-dimensional shape of molecule / sizes of atoms relative to their bonds

85
Q

Relative formula mass symbol?

A

Mr

86
Q

To calculate the Mr of a substance you

A

Add together all the relative atomic masses of all the atoms shown in its formula

87
Q

Relative formula mass of oxygen molecule?

A

O relative atomic mass = 16
O2 = 16 x 2
= 32

88
Q

What’s is Mr units?

A

It has no units
Mr values are just numbers

This is because an Mr value is the mass of a molecule or unit of a substance compared with 1/12thxthe mass of a 12C atom. The M in Mr stands for ‘molecular’

You might see or hear the term ‘relative molecular Mass’ this really applies only to covalent substances

89
Q

How do you calculate an empirical formula

A 
Symbol 
Mass of each element in g 
Ar of each element 
Mass/Ar 
Divide each by smallest 
May need to multiply to rid fractions
90
Q

You can find the molecular formula of a compound from its empirical formula :
If you know it’s relative formula mass Mr

A

Calculate Mr or empirical formula
Divide Mr of X by answer 1
Multiply each by empirical formula

91
Q

How do you determine the empirical formula experiment

A

Him

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