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CHEMISTRY > Topic 9 > Flashcards

Topic 9 Flashcards

1
Q

What’s a crude oil

A

Fossil fuel formed over millions of years from ancient remains of marine

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2
Q

What’s a hydrocarbon

A

Compound of carbon and hydrogen atoms only. Carbon atoms can form four covalent bonds

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3
Q

In a hydrogen molecule the four bonds that carbon can make are

A

Carbon-carbon
And
Carbon-hydrogen

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4
Q

Hydrocarbon molecules can consist of

A

Chains (with or without branches) or rings of carbon atoms

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5
Q

Crude oil is a complex mixture of

A

Hydrocarbons with their carbon atoms in chains or rings

An important source of useful substances

A finite resource

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6
Q

What does finite resources

A

They are no longer being made

Being made extremely slowly

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7
Q

How long does crude oil take to form

A

Millions of years

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8
Q

What’s the formula for crude oil

A

C2H6

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9
Q

Describe two ways in which crude oil is an important source of useful substances

A

Hydrocarbons from crude oil are useful as fuels and as feedstock for the petrochemical industry

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10
Q

What fuels come from crude oil

A

Petrol and diesel

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11
Q

What’s feedstock

A

Is a starring material for an industrial chemical process

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12
Q

The petrochemical industry involves

A

The use and manufacture of substances from crude oil

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13
Q

Exothermic reaction

A

Heat energy is given out and the reaction mixture or the surroundings increase in temperature

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14
Q

Endothermic reaction

A

Heat energy is taken in

The reaction mixture or the surrounds decrease in temperature

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15
Q

What apparatus can you use to investigate the temperature changes in reactions

A 
Thermometer 
Lid with hole 
Polystyrene cup 
Breaker for support 
Reaction mixture

The healer and air inside are further insulation to reduce energy transfer

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16
Q

When a chemical reaction happens the bonds that hold the atoms together in the molecules of the tea tents are

A

Broken

The atoms then come together in new arrangements to form the products

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17
Q

In exothermic reactions energy is

A

Released to surroundings cause more heat energy is released making bonds in products than is needed to break bonds in reactants

Overall energy is released to surroundings and this makes the reaction exothermic

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18
Q

In an endothermic reaction energy is taken in from the surroundings because

A

Less heat energy is released making bonds in the products than is needed to break bonds in the reactants

Overall energy is taken in to the reaction and this makes it endothermic

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19
Q

Calcium chloride is added to water and stirred

Explain why the mixture warms up

A

An exothermic chanhenhappens

More heat energy is released in forming bonds in the products than is needed to break bonds in the reactants
So overall heat energy is given out

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20
Q

Breaking bonds is e

A

Endothermic

Energy needed

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21
Q

Making bonds is

A

Exothermic

Energy is released

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22
Q

Exothermic reaction profiles

A

Energy of reactants is greater than energy of products

Energy changes of reaction is negative

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23
Q

What is activation energy (exothermic reactions)

A

Minimum energy needed to start a reaction it may be supplied by fornexample:

Heating the reaction mixture

Applying a flame or spark

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24
Q

Endothermic reaction profile

A

Energy level of reactants is lower than energy level of products

Energy change of reaction is positive

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25
Q

Activation energy for endothermic reactions could be supplied by

A

Continually heating the reaction mixture

Passing an electric current though an electrolyte (electrolysis)

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26
Q

What is a bond energy

A

The energy needed to break 1 mol of a particular covalent bond, for example

413 kJ is needed to break 1 mol of C-H bonds

413 kJ is needed when 1 mol of C-H bonds forms

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27
Q
  • energy change =
A

Exothermic

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28
Q

Fractional distillation is used to separate

A

Crude oil into simpler, more useful mixtures

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29
Q

Why can crude oil be separated by fractional distillation

A

Because of its different hydrocarbons have different boiling points

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30
Q

What happens to crude oil during fractional distillation

A

Oil is heated to exaporate it
Vapours rise in a fractionating column
The column has a temperature gradient- hot at the bottom, cool at the top
Each fraction condenses where it becomes cool enough and is piped out of the column

The gases fraction does not
Condense and leaves at the top

The bitumen fraction does not evaporate and leaves at the bottom

The other fractions are liquid at room temperature and are useful as fuels

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31
Q

What is a fraction?

A

A mixture of hydrocarbons with similar boiling points and numbers of carbon atoms

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32
Q

Most of the hydrocarbons from crude oil are

A

Alkanes

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33
Q

What are alkanes

A

A homologous series of hydrocarbons

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34
Q

As the number of carbon and hydrogen atoms in a hydrogen molecule increases :

A

The strength of the intermolecular forces increases

More energy must be transferred to overcome these forces

The boiling point increases

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35
Q

Name the fractions of crude oil

A 
Gases 
Petrol
Kerosene 
Diesel oil 
Fuel oil
Bitumen
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36
Q

Use of gases

A

Domestic heating and cooking

37
Q

Use of petrol

A

Fuel for cars

38
Q

Use of kerosene

A

Fuel for aircraft

39
Q

Use of diesel oil

A

Fuel for some cars and trains

40
Q

Use of fuel oil

A

Fuel for large ships and some power stations

41
Q

Use of bitumen

A

Surface roads and roofs

42
Q

What is a homologous series??

A

A series of compounds :

  • in which molecular formulae of neighbouring members differ by CH2
  • that show a gradual variation in physical properties, such a boiling points
  • that have similar chemical properties
43
Q

Alkanes undergo

A

Complete combustion

44
Q

When alkanes react completely with oxygen whatbare formed?

A

Carbon dioxide and water vapour

45
Q

Methane is from

A

Natural gas

46
Q

Formula for methane

A

CH4

47
Q

Methane+ oxygen ->

A

Carbon dioxide + water

48
Q

Names of alkanes

A

End in ane

Ethane
Propane

49
Q

Structure of alkanes

A

Single bonds only

50
Q

Formulae and reactions of alkanes

A

General formula is

C2H2n+2

They are flammable and form carbon dioxide and water when they completely burn

C2H6
C3H8

51
Q

Features of a homologous series

A

Same general formula

Molecular formulae of neighbouring members differ by CH2

Gradual variation in physical properties

Similar chemical properties

52
Q

When does incomplete combustion happen?

A

When the supply of oxygen to a burning fuel is limited

53
Q

During complete combustion of a

Hydrocarbon fuel, such as petrol, kerosene or diesel oil :

A

Hydrogen is oxidised to water vapour

Carbon is oxidised to carbon dioxide

Energy is given out (transferred to the surroundings by radiation as heat and light)

54
Q

During incomplete combustion, hydrogen is still oxidised to water vapour but

A

Carbon may be partially oxidised to carbon monoxide, CO

Carbon may be released as carbon particles or soot

Less energy is given out

55
Q

During incomplete combustion, different amounts of the different carbon products form, depending on how much oxygen is available for oxidation for example

A

Methane + oxygen -> carbon + carbon monoxide + carbon dioxide + water

56
Q

Cars and appliances

A

There is always incomplete combustion in vehicles engine

CO2 C CO H2O

Faulty gas boilers can produce carbon monoxide and soot

Working normally - CO2 H2O
Faulty - CO2 CO C H2O

57
Q

Explain how carbon monoxide behaves as a toxic gas

A

Carbon monoxide attaches to haemoglobin in red blood cells, preventing oxygen attaching instead
This reduced the amount of oxygen carried around the body by bloodstream

58
Q

Describe two problems caused by soot

A

Soot can build up in chimneys where it is may eventually cause fires ; it also blackens buildings

59
Q

Carbon monoxide can cause unconsciousness and even death it is:

A

Colourless
Odourless

Electronic carbon monoxide detectors are used to warn us when the gas is present

60
Q

Tiny soot particles can be breathed in this may cause

A

Lung diseases such as bronchitis or make existing lung diseases worse

61
Q

Explain why soot and carbon monoxide are produced during incomplete combustion of a hydrocarbon fuel

A

There is a poor supply of air/oxygen
So carbon in the fuel is only partially oxidised to carbon monoxide
Or released as carbon particles/soot

62
Q

Explain why carbon monoxide is difficult for our bodies to detect

A

It is odourless and colourless

63
Q

A householder sees soot marks around his gas boiler
He thinks that this shows that carbon monoxide is being produced

Comment on the accuracy of this thought

A

Soot shows that incomplete combustion is happening
Carbon monoxide might be forming but soot does not prove this/carbon monoxide is likely to be forming as well (which could be confirmed using a carbon monoxide detector)

64
Q

Rainwater is naturally

A

Acidic

65
Q

Acid rain is more

A

Acidic than normal

66
Q

Hydrocarbon fuels may contain

A

Impurities such as Sulfur compounds

67
Q

When the fuel burns the fulfil in these impurities is oxidised to form sulfur dioxide

A

Sukfur + oxygen -> sulfur dioxide

Sulfur dioxide is a non-metal oxide
It dissolved in rainwater to form an acidic solution

68
Q

The problems caused by acid rain can be reduced in several ways including :

A

Removing Sulfur from petrol, diesel oil and fuel oil at the oil refinery before selling it

Preventing sulfur dioxide leaving power station chimneys - “flue has desulfurisation”

Adding calcium carbonate or calcium hydroxide to fields and lakes to neutralise excess acid from acid rain

69
Q

The effects of acid rain

A

Rivers lakes and souls are more acidic which harms organisms living in them

Trees are damaged

Acid rain speeds up the weathering of buildings and statues

Waste gases from power stations and vehicles contain sulfur dioxide

Sulfur dioxide dissolved in water in the air

70
Q

Oxides of nitrogen NOx are atmospheric pollutants. They may contribute to acid rain

Explain why oxides of nitrogen are produced when hydrocarbon fuels are used in vehicle and aircraft engines

A

Air goes into the engine so that the fuel can burn. Nitrogen and oxygen from the air react together at the Hugh temperature in the engine to produce oxides of nitrogen

71
Q

Unlike sulfur dioxide oxides of nitrogen ar enot produces from

A

Impurities in the hydrocarbon fuel

NO2 is a nonmetal oxide that dissolved in rainwater to form an acidic solution

72
Q

Nitrogen dioxide is a toxic

A

Orange-brown gas

Sharp smell

73
Q

Most cars use petrol or diesel oil but hydrogen may also be used as a

A

Fuel for cars

74
Q

These fossil fuels are obtained from crude oil:

A

Petrol
Diesel oil
Fuel oil

75
Q

This fossil fuel is obtained from natural gas:

A

Methane

76
Q

Non-renewable sources are

A

Used up faster than they are formed

77
Q

Crude oil and natural gas take millions of years to form. The fossil fuels abotsined from these resources are

A

Being used up very quickly so they are non-renewables fuels

78
Q

The combustion of hydrogen produces only water vapour

A

Hydrogen + water -> water

79
Q

Hydrogen is manufactured in several ways- including

A

Electrolysis of water

Cracking of oil fractions

Reaction of natural gas Waugh steam
CH4 + 2H2O -> CO2 + 4H2

80
Q

Three features of a good fuel

A

Burn easily - easy to ignite and stay alight

Not produces soot smoke or ash

Release a lot of energy when it burns

Easy to store and transport safely

81
Q

Petrol vs hydrogen

A

Both burn easily

Petrol doesn’t produce ash
Hydrogen does not produce ash or smoke

Petrol produces carbon dioxide and carbon monoxide as well as water when it burns:(
Hydrogen only produces water when t burns:)

Petrol releases more energy per kg when it burns than fuels such as coal or wood
Hydrogen releases nearly three times as much as energy per kg as petrol

Petrol is a liquid so it is easy to store and transport
Hydrogen is a gas so it has to be stored at high pressure :(

filling stations oils need to be adapted for hydrogen to be used in cars:(

82
Q

Explain why the combustion of petrol produces carbon dioxide but the combustion of hydrogen does not

A

Petrol contains hydrocarbons
The carbon in these molecules is oxidised to carbon dioxide
Hydrogen does not contain carbon/consists only of hydrogen

83
Q

Suggest reasons to explain why hydrogen produces from crude oil or natural gas may not be renewable

A

Xcruse oil and natural gas are non renewable they are being used faster than they are formed

84
Q

CO2 is a greenhouse gas lined to global warming and climate change

Hydrogen is often regarded as a “carbon-neautral fuel” a fuel with production transport and use that have no overal emmistion of carbon dioxide

Suggest reasons to explain why hydrogen may not actually by carbon neutral

A

Carbon dioxide may be produced during the manufacture or transport of the fuel

Eg fossil fuels are used in power stations to generate electricity to react with steam to make hydrogen

85
Q

What is cracking

A

A process carried out on fractions in oil refineries after fractional distillation

86
Q

What does cracking involve

A

Breaking down larger alkanes into smaller, more useful alkanes and alkanes

87
Q

Cracking does from

A

Cracking breaks down long molecules by heating them

Producing shooter chain alkanes which are useful as fuels and
Alkanes which are used to make polymers

88
Q

Cracking in the lab

A

Paraffin is an alkane
Liquid paraffin can be cracked in the lavatory using this apparatus

The porous pot catalyst is heated strongly

The liquid paraffin is heated and evaporated

The paraffin is heated and evaporated

The paraffin vapour passed over the hot porous pot and the hydrocarbon molecules break down

One of the products is ethene which is a gas and collects in the other tube

89
Q

Explain how cracking helps to balance supply with demand

A

Some larger alkanes such as bitumen are in greater supply than their demand
Cracking coverage this alkanes into smaller hydrocarbons such as petrol which are in greater demand than can be supplied by fractional distillation alone

CHEMISTRY (15 decks)

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