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Chemistry revision > Topic 8- fuels > Flashcards

Topic 8- fuels Flashcards

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1
Q

What are hydrocarbons

A

A compound that contains carbon and hydrogen only

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2
Q

Describe a crude oil- 5 points

A

A complex mixture of hydrocarbons
Containing molecules in which carbon atoms are in chains or rings
An important source of useful substances (fuels and feed stock for the petrochemical industry)
A finite resource
Non renewable

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3
Q

How do we separate crude oil

A

We separate crude oils into simpler more useful mixtures by the process of fractional distillation

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4
Q

List the fractions in fractional distillation, in order from top to bottom (lowest bp to highest bp)

A 
Gases
Petrol
Kerosene
Diesel oil 
Fuel oil 
Bitumen
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5
Q

Recall the names and uses of the fractions from top to bottom (lowest bp to highest bp)

A

Gases- domestic heating and cooking
Petrol- Fuel in cars
Kerosene- Fuel for aircraft
Diesel oil- fuel for some cars and trains
Fuel oil- fuel for large ships and in some power stations
Bitumen-used to surface roads and roofs

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6
Q

What is fractional distillation

A

A tall fractionating column is fitted above the mixture, with several condensers coming off at different heights. The column is hot at the bottom and cool at the top. Substances with high boiling points condense at the bottom and substances with lower boiling points condense on the way to the top.

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7
Q

List how hydrocarbons in different fractions differ from each other

A

The number of carbon and hydrogen atoms their molecules contain
boiling points
ease of ignition
viscosity
and are all mostly members of the alkAne homologous series.

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8
Q

Explain a homologous series as a series of compound which…

A

Have the same general formula
Differ by CH2 in molecular formula from neighboring compounds
Show a gradual variation in physical properties, as exemplified by their boiling points
Have similar chemical properties

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9
Q

Describe the complete combustion of hydrocarbon fuels as a reaction in which…

A

Carbon dioxide and water are produced

Energy is given out

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10
Q

What is incomplete combustion

A

incomplete combustion occurs when the supply of air or oxygen is poor. Water is still produced, but carbon monoxide and carbon are produced instead of carbon dioxide.

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11
Q

Explain why the incomplete combustion of hydrocarbons can produce carbon and carbon monoxide

A

Part of the carbon is not completely oxidised which therefore produces soot or carbon monoxide.

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12
Q

How does carbon monoxide behave as a toxic gas

A

When breathed in it displaces the oxygen in the blood, the bond between carbon monoxide and haemoglobin is so much stronger than the bond with oxygen. Oxygen is then unable to access vital organs and destroys cells.

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13
Q

Describe the problems caused by incomplete combustion producing carbon monoxide and soot in appliances that use
carbon compounds as fuels

A

It blocks pipes carrying waste gases from an appliance and blacken/ stain buildings- soot

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14
Q

What can impurities in some hydrocarbon fuels result in and why

A

Most hydrocarbon fuels burnt aren’t pure and therefore naturally contain some sulfur compounds (impurities). When the fuel burns, the sulfur it contains is oxidised to sulfur dioxide

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15
Q

How does sulfur dioxide cause acid rain and what are some problems associated with acid rain

A

Sulfur dioxide dissolves in water droplets in clouds, this makes the rain more acidic. Acid rain reacts with metals and rock such as limestone (corrodes them) Makes soil and water acidic which kills off wildlife.

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16
Q

Why, when fuels are burned in engines can oxygen and nitrogen react together at high temperatures

A

At high temperatures nitrogen and oxygen from the air combine to produce nitrogen monoxide and other oxides. Coal is made mainly from carbon, when this burns carbon dioxide is produced. When nitrogen monoxide is released the vehicles exhaust system combines it with oxygen in the air to form nitrogen dioxide. ????

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17
Q

Evaluate the advantages and disadvantages of using hydrogen, rather than petrol as a fuel in cars

A

Hydrogen doesn’t generate carbon dioxide when burnt
Hydrogen fuel cells are very efficient
HOWEVER
There are few filling stations that sell hydrogen
Hydrogen must be compresses and liquefies, then stored in tough insulated fuel tanks
Hydrogen fuel cells do not work at very low temperatures and they may require a platinum catalyst which is very expensive

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18
Q

List the non renewable fossil fuels obtained from crude oil and an example of a non renewable fossil fuel found in natural gas

A

petrol, kerosene and diesel oil are non-renewable
fossil fuels obtained from crude oil and methane is a nonrenewable
fossil fuel found in natural gas

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19
Q

What does Cracking involve

A

Breaking down a larger saturated hydrocarbon molecule ( alkAnes) into smaller, more useful ones, some of which are unsaturated (alkEnes)

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20
Q

Why is cracking necessary

A

To match supply with demand

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21
Q

What are the differences between alkAnes and alkEnes?

A

AlkAnes- Saturated, form a single bond C-C

AlkEnes- Unsaturated, form a double bond C=C

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22
Q

Whats the equation for complete combustion

A

Hydrocarbon+Oxygen–> Carbon Dioxide + Water

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23
Q

Whats the equation for incomplete combustion

A

Hydrocarbon+Oxygen—> Carbon monoxide+Carbon+Water

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24
Q

What’s the general formula for AlkAnes

A

CnH2n+2

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25
Q

What’s the general formula for alkEnes

A

CnH2n

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26
Q

What names are there for the number of Carbons.

A 
Meth 1
Eth 2
Prop 3 
But 4
Pent 5 
Hex 6
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27
Q

In alkanes what does a longer chain mean

A

A higher boiling/melting point

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28
Q

Can alkanes do addition reactions

A

They are saturated and only have single bonds (everything has something attached) therefore they cannot

29
Q

Can alkEnes react

A

Yes because they are unsaturated, there is room for addition of molecules

30
Q

What happens when you react an alkAne with bromine water

A

The product retains the colour from the bromine solution (brown orange)

31
Q

What happens when you react an alkEne with bromine water

A

The product is colourless

32
Q

What is cracking

A

A chemical reaction in which large alkane molecules are split into 2 or more small alkanes and alkEnes

33
Q

What can decane be cracked to for,

A

Octane and ethene

34
Q

Give an explanation of the practical using paraffin oil in cracking

A

When paraffin oil is heated, it evaporates to form a gas. The paraffin gas passes over the hot pieces of porous pot. The heat causes some of the covalent bonds in the paraffin to break so the paraffin is cracked. An alkane with a shorter carbon chain is formed, ethene is also formed. It’s a gas so collects in the test tube

35
Q

Why were first few bubbles of gas allowed to escape

A

They were just air from the boiling tube

36
Q

What does a catalyst do

A

Lower activation energy

37
Q

What is paraffin

A

Long hydrocarbon

38
Q

What happens when the heat is removed

A

The gas left in the apparatus contacts.
If the end of the delivery tube is still under water the water will he forced up into the hot tube and the tube will crack, this is called suck back

39
Q

What are alcohols

A

Organic molecules with a framework of carbon atoms to which hydrogen and other atoms are attached

40
Q

What is the functional group of alcohols

A

-OH

41
Q

What do all the names of alcohols end in

A

Anol

42
Q

What’s the formula for ethanol

A

C2H5OH

43
Q

What are carboxylic acids

A

A homologous series which all have the functional group- COOH
One of the oxygen in the group is joined to the carbon atom with a double bond

44
Q

How do we make carboxylic acids

A

Oxidising alcohols

Ethanol + oxygen- ethanoic acid + water

45
Q

What do smaller chains do

A

Dissociate more (more readily) as they have less bonds to break

46
Q

What does a metal and an acid always produce

A

Hydrogen

47
Q

What are polymers

A

Substances of high average relative molecular mass made up of small repeating units called monomers

48
Q

What is a polymerisation reaction

A

Lots of monomers join up to make a polymer

49
Q

Give 3 examples of synthetic polymers

A

Poly(ethene) made from Ethene monomers
Poly(propene) made from propene monomers
Poly(chloroethene) chloroethene

50
Q

Give 3 examples of natural polymers

A

Starch- made from glucose
DNA- made from nucleotides
Protein- made from amino acids

51
Q

Because the number of carbon atoms can vary we cannot give a formula for a polymer molecule how do we show addition polymerisation

A

Find the repeating unit
Opening the double bond and expanding the double bracket through
Put an n in the corner

52
Q

What are the properties and uses of polyethene

A

Flexible cheap and good insulator

Used for plastic bags, bottles, cling film and polytunnels

53
Q

What are the properties and uses of polypropylene

A

Flexible does not shatter

Used for buckets, bowls, crates, ropes and carpets

54
Q

What are the properties and uses of polychloroethene (pvc)

A

Tough good insulator can be made hard or flexible

Used for window frames, gutters, pipes, insulation for electrical wires

55
Q

What are the properties and uses of poly tetrafluoroethene (ptfe/ teflon)

A

Tough and slippery

Used for non stick coatings on frying pans and kitchen utensils, Burette taps, stain proofing clothing and carpets

56
Q

How is poly(chloroethene) formed

A

Lots of chloroethene monomers joined up to make a long molecule

57
Q

What is condensation polymerisation

A

Condensation polymerisation usually involves two different types of monomer.
The monomers react together and bonds form between them, making polymer chains.
Each monomer has to contain at least two functional groups, one on each end of the molecules.
Each functional group can react with the functional group of another monomer, creating long chains of alternating monomers. For each new bond that forms, a small molecule (e.g. Water) is lost.

58
Q

What does condensation polymerisation make

A

Water

59
Q

What happens when ethanol and ethanoic acid join

A

A molecule of water is Eliminated, the organic molecule formed is an ester called ethyl ethanol

60
Q

What happens when ester bonds form

A

Water forms

61
Q

What parts of molecules join to form the water

A

The -OH part of the carboxylic acid functional group and the H atom from alcohol functional group
The only remaining parts of the carboxylic acid and alcohol molecules join up to form an ester

62
Q

What do all esters contain

A

A coo link

A carbon double bonded to an oxygen and then a single bond to an oxygen

63
Q

What do you need to form a polyester

A

A carboxylic acid
An alcohol
Which both have functional group at both ends so they can join together to form H20

64
Q

What is most polymer waste

A

Non biodegradable

65
Q

Advantage and disadvantages of landfill

A

Maybe possible to extract and sell the methane produced
But
What uses valuable land and harmful substances leak into soil and water supply

66
Q

Advantage and disadvantages of incineration

A

Produces useful energy
But
May produce harmful or toxic gases

67
Q

Advantage and disadvantages of recycling

A

New items can be made, conserves supply of crude oil
But
Polymers need to be melted and items need to be collected, stored and washed

68
Q

What forms when carboxylic acid monomers and alcohol monomers react together

A

Polyesters form

Chemistry revision (10 decks)

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