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Chemistry 21st century > Chemicals of the Natural Environment. > Flashcards

Chemicals of the Natural Environment. Flashcards

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1
Q

What does dry air contain?

A

A mixture of non metal elements and compounds eg N2, O2, Ar, CO2

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2
Q

What is Ar?

A

Argon, a noble gas.

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3
Q

What percentage of dry air is oxygen?

A

21%

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4
Q

What percentage of dry air is nitrogen?

A

78%

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5
Q

What percentage of dry air is argon?

A

1%

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6
Q

What percentage of dry air is carbon dioxide?

A

0.04%

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7
Q

How are the molecules in the air held together?

A

Covalent bonds.

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8
Q

How does a covalent bond form?

A

Atoms share a pair of electrons.

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9
Q

How does that hold the atoms together?

A

Both positive nuclei are attracted by the electron cloud between them.

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10
Q

What sort of boiling and melting points do simple molecules have?

A

Very low, eg N2 -210C and -196C

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11
Q

Why do these small molecules have such low melting and boiling points?

A

The attractive forces between the molecules are very weak, so very little energy is required for them to move apart.

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12
Q

Why can’t pure molecular substances conduct electricity?

A

They are electrically neutral, and there are no free electrons.

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13
Q

How strong are the forces within the molecules for these small molecules like O2?

A

Very strong.

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14
Q

What happens when a molecular substance melts?

A

The molecules are separated from one another, but the covalent bonds are not broken.

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15
Q

What is the name given to all the water on earth?

A

The earth’s hydrosphere

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16
Q

What does the hydrosphere consist of?

A

Mainly water, with some dissolved ionic compounds called salts.

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17
Q

How are the ions in an ionic solid arranged?

A

In a giant regular 3D pattern called a lattice.

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18
Q

What is the name given to the force of attraction between positive and negative ions?

A

Ionic bond

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19
Q

Why do ionic compounds not conduct electricity when they are solid?

A

The ions are not free to move.

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20
Q

Why do ionic compounds conduct electricity when in solution, or molten?

A

The ions are free to move.

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21
Q

Why would it be true to say that ionic compounds only exist in the solid state?

A

When they are liquid or aqueous the ions are all moving independently, they are not moving as a pair.

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22
Q

What is the overall charge on an ionic compound?

A

Neutral

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23
Q

What do you call an ion made up of a group of atoms, eg OH-

A

A molecular ion

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24
Q

What is the charge on the SO4 ion?

A

2-

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25
Q

What is the charge on the OH ion?

A

-

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26
Q

What is the charge on the CO3 ion?

A

2-

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27
Q

What is the charge on the NO3 ion?

A

-

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28
Q

What colour are many salts of copper when in solution?

A

Blue

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29
Q

How can an insoluble precipitate be used to identify an ionic compound?

A

The colour of the precipitate can be distinctive.

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30
Q

What happens if you add sodium hydroxide to a calcium salt?

A

You get a white precipitate (insoluble in excess)

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31
Q

What happens if you add sodium hydroxide to a copper salt?

A

You get a light blue precipitate (insoluble in excess)

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32
Q

What happens if you add sodium hydroxide to an iron (II) salt?

A

You get a green precipitate (insoluble in excess)

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33
Q

What happens if you add sodium hydroxide to an iron (III) salt?

A

You get a red-brown precipitate (insoluble in excess)

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34
Q

What happens if you add sodium hydroxide to a zinc salt?

A

You get a white precipitate (soluble in excess)

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35
Q

How could you identify the carbonate ion?

A

Add dilute acid and look for effervescence (fizzing)

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36
Q

What is the name for the outer layer of the earth, made up of the crust and upper mantle?

A

The lithosphere.

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37
Q

What is the lithosphere made of?

A

Rocks and minerals

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38
Q

What are minerals?

A

Solids with ions or atoms arranged in a regular structure or lattice.

39
Q

What are the abundant elements in the lithosphere?

A

Silicon, oxygen, aluminium

40
Q

Where are most of the silicon and oxygen on earth found?

A

Joined together as SO2 in rocks, eg quartz

41
Q

What is a rock containing a metal called?

A

An ore

42
Q

How can you extract the metal if the metal ore is an oxide?

A

Copper, zinc and iron are all heated with carbon, which reduces the metal by taking away the oxygen

43
Q

How much metal is there in an ore?

A

It varies, sometime huge amounts of ore give only small amounts of metal - eg copper.

44
Q

What sort of reaction is the heating of metal oxide with carbon?

A

Redox, as both reduction and oxidation happen

45
Q

What is reduction?

A

Losing oxygen

46
Q

What is oxidation?

A

Gaining oxygen

47
Q

What element makes up diamond and graphite?

A

Carbon

48
Q

What is the structure of both diamond and graphite?

A

Many carbon atoms are bonded together in a regular pattern.

49
Q

What would you call it when many atoms are covalently bonded together in a regular structure?

A

A giant covalent structure.

50
Q

What is the shape of the lattice in diamond?

A

Each carbon atom is surrounded by 4 other carbon in the shape of a tetrahedron, this is a very strong structure.

51
Q

What is the shape of the lattice in graphite?

A

The carbon is arranged in hexagons, which form layers. This structure breaks easily along the layers. (And conducts electricity).

52
Q

Why does graphite conduct electricity?

A

There are free moving electrons between the layers of hexagons.

53
Q

Which is the only covalently bonded substance that can conduct electricity?

A

Graphite.

54
Q

What do you call the chemicals that react together?

A

The reactants.

55
Q

What do you call the chemicals that are made?

A

The products.

56
Q

What does a chemical equation show?

A

The reactants and the products.

57
Q

What does a balanced chemical equation show?

A

The numbers of atoms on each side of the equation, these must be equal.

58
Q

What do the state symbols show?

A

The state of each of the substances, solid (s), liquid (l), gas (g), or dissolved in water (aq)

59
Q

What is the relative atomic mass of an atom?

A

The mass of an atom compared to an atom of carbon 12, which is given the value of 12.

60
Q

What is the relative formula mass of a compound?

A

The sum of the relative masses of all of its atoms or ions.

61
Q

What is the gram formula mass of a compound?

A

The relative formula mass in grammes. So, for water, H2o, we add up 1+1+16 = 18, so 18g

62
Q

How can you work out the percentage of an element in a compound?

A

Take the relative mass of the element, divide by relative mass off the compound, then multiply by 100

63
Q

What is the percentage iron in Fe2O3 (use your periodic table)?

A

70%

64
Q

How much iron can you get from 160 grammes of Fe2O3?

A

112g

65
Q

What does the word electrolysis mean?

A

Splitting with electricity - used to mean passing an electric current through a solution of an ionic compound, or a molten ionic compound, and splitting it.

66
Q

Why is the ionic compound called an electrolyte?

A

because it conducts electricity and splits.

67
Q

How can you make aluminium from aluminium oxide?

A

Electrolysis

68
Q

What is produced at the anode when aluminium oxide is electrolysed?

A

Oxygen

69
Q

Why does aluminium oxide need to be electrolysed rather than using a redox reaction with carbon?

A

Carbon can’t take the oxygen from aluminium, the aluminium is too reactive.

70
Q

How many electrons would the Al3+ ion gain?

A

3

71
Q

How many electrons would each O2- ion lose?

A

2

72
Q

Is aluminium a cation or an anion?

A

Cation

73
Q

Why are metals useful?

A

They are strong, malleable (they can be hammered into shape), have high melting points and can conduct electricity.

74
Q

What bonds hold the atoms in metals together?

A

Metallic bonds

75
Q

How are the atoms in metals arranged?

A

In a giant lattice

76
Q

What do metals lose to form ions?

A

Their outer shell electrons.

77
Q

What happens to the electrons in solid metals?

A

They form a “sea of electrons” which can move freely

78
Q

Is the attraction between the positive atoms and the sea of electrons strong or weak? (Hint - think about the melting point of metals)

A

Strong

79
Q

In a pure metal, all the atoms are the same size. True or false?

A

True

80
Q

When a metal is reshaped, what do the atoms do?

A

Roll over each other.

81
Q

Metal is easily reshaped, the word for this is?

A

Malleable

82
Q

What property of metals can make them very dangerous to the environment?

A

They are poisonous, eg lead, mercury, cadmium.

83
Q

What do waste poisonous metals from mines do?

A

Destroy habits, damage soil, pollute water sources.

84
Q

What does extracting metal create that causes acid rain?

A

Pollutant gases

85
Q

Large amounts of some ores need to be processed to get very small amounts of metal. True or false?

A

True

86
Q

Processing large amounts of rock requires large amounts of ….?

A

Energy

87
Q

If the ore contains a compound of metal and sulfur, what pollutant is likely to be made during the extraction of the metal?

A

SO2

88
Q

What does SO2 form with water?

A

H2SO3 (sulfurous acid)

89
Q

What water would SO2 in the atmosphere react with?

A

Rain

90
Q

What would be the pH of rain that contains H2SO3?

A

Less than 7, acid

91
Q

Why do we need large amounts of copper?

A

It is used for electrical wiring (very low resistance) and water pipes.

92
Q

What poisonous metals did car batteries once contain?

A

Pb (lead)

93
Q

What metal does modern batteries contain?

A

Lithium

94
Q

Why is using lithium in batteries a problem?

A

It is hard to get enough lithium

Chemistry 21st century (10 decks)

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