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CHEMISTRY > Topic 9 > Flashcards

Topic 9 Flashcards

(89 cards)

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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
Activation energy for endothermic reactions could be supplied by
Continually heating the reaction mixture Passing an electric current though an electrolyte (electrolysis)
26
What is a bond energy
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
27
- energy change =
Exothermic
28
Fractional distillation is used to separate
Crude oil into simpler, more useful mixtures
29
Why can crude oil be separated by fractional distillation
Because of its different hydrocarbons have different boiling points
30
What happens to crude oil during fractional distillation
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
31
What is a fraction?
A mixture of hydrocarbons with similar boiling points and numbers of carbon atoms
32
Most of the hydrocarbons from crude oil are
Alkanes
33
What are alkanes
A homologous series of hydrocarbons
34
As the number of carbon and hydrogen atoms in a hydrogen molecule increases :
The strength of the intermolecular forces increases More energy must be transferred to overcome these forces The boiling point increases
35
Name the fractions of crude oil
``` Gases Petrol Kerosene Diesel oil Fuel oil Bitumen ```
36
Use of gases
Domestic heating and cooking
37
Use of petrol
Fuel for cars
38
Use of kerosene
Fuel for aircraft
39
Use of diesel oil
Fuel for some cars and trains
40
Use of fuel oil
Fuel for large ships and some power stations
41
Use of bitumen
Surface roads and roofs
42
What is a homologous series??
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
Alkanes undergo
Complete combustion
44
When alkanes react completely with oxygen whatbare formed?
Carbon dioxide and water vapour
45
Methane is from
Natural gas
46
Formula for methane
CH4
47
Methane+ oxygen ->
Carbon dioxide + water
48
Names of alkanes
End in ane Ethane Propane
49
Structure of alkanes
Single bonds only
50
Formulae and reactions of alkanes
General formula is C2H2n+2 They are flammable and form carbon dioxide and water when they completely burn C2H6 C3H8
51
Features of a homologous series
Same general formula Molecular formulae of neighbouring members differ by CH2 Gradual variation in physical properties Similar chemical properties
52
When does incomplete combustion happen?
When the supply of oxygen to a burning fuel is limited
53
During complete combustion of a | Hydrocarbon fuel, such as petrol, kerosene or diesel oil :
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
During incomplete combustion, hydrogen is still oxidised to water vapour but
Carbon may be partially oxidised to carbon monoxide, CO Carbon may be released as carbon particles or soot Less energy is given out
55
During incomplete combustion, different amounts of the different carbon products form, depending on how much oxygen is available for oxidation for example
Methane + oxygen -> carbon + carbon monoxide + carbon dioxide + water
56
Cars and appliances
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
Explain how carbon monoxide behaves as a toxic gas
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
Describe two problems caused by soot
Soot can build up in chimneys where it is may eventually cause fires ; it also blackens buildings
59
Carbon monoxide can cause unconsciousness and even death it is:
Colourless Odourless Electronic carbon monoxide detectors are used to warn us when the gas is present
60
Tiny soot particles can be breathed in this may cause
Lung diseases such as bronchitis or make existing lung diseases worse
61
Explain why soot and carbon monoxide are produced during incomplete combustion of a hydrocarbon fuel
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
Explain why carbon monoxide is difficult for our bodies to detect
It is odourless and colourless
63
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
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
Rainwater is naturally
Acidic
65
Acid rain is more
Acidic than normal
66
Hydrocarbon fuels may contain
Impurities such as Sulfur compounds
67
When the fuel burns the fulfil in these impurities is oxidised to form sulfur dioxide
Sukfur + oxygen -> sulfur dioxide Sulfur dioxide is a non-metal oxide It dissolved in rainwater to form an acidic solution
68
The problems caused by acid rain can be reduced in several ways including :
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
The effects of acid rain
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
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
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
Unlike sulfur dioxide oxides of nitrogen ar enot produces from
Impurities in the hydrocarbon fuel NO2 is a nonmetal oxide that dissolved in rainwater to form an acidic solution
72
Nitrogen dioxide is a toxic
Orange-brown gas | Sharp smell
73
Most cars use petrol or diesel oil but hydrogen may also be used as a
Fuel for cars
74
These fossil fuels are obtained from crude oil:
Petrol Diesel oil Fuel oil
75
This fossil fuel is obtained from natural gas:
Methane
76
Non-renewable sources are
Used up faster than they are formed
77
Crude oil and natural gas take millions of years to form. The fossil fuels abotsined from these resources are
Being used up very quickly so they are non-renewables fuels
78
The combustion of hydrogen produces only water vapour
Hydrogen + water -> water
79
Hydrogen is manufactured in several ways- including
Electrolysis of water Cracking of oil fractions Reaction of natural gas Waugh steam CH4 + 2H2O -> CO2 + 4H2
80
Three features of a good fuel
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
Petrol vs hydrogen
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
Explain why the combustion of petrol produces carbon dioxide but the combustion of hydrogen does not
Petrol contains hydrocarbons The carbon in these molecules is oxidised to carbon dioxide Hydrogen does not contain carbon/consists only of hydrogen
83
Suggest reasons to explain why hydrogen produces from crude oil or natural gas may not be renewable
Xcruse oil and natural gas are non renewable they are being used faster than they are formed
84
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
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
What is cracking
A process carried out on fractions in oil refineries after fractional distillation
86
What does cracking involve
Breaking down larger alkanes into smaller, more useful alkanes and alkanes
87
Cracking does from
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
Cracking in the lab
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
Explain how cracking helps to balance supply with demand
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

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