Topic 8- fuels

Question 1

What are hydrocarbons

Answer 1

A compound that contains carbon and hydrogen only

Question 2

Describe a crude oil- 5 points

Answer 2

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

Question 3

How do we separate crude oil

Answer 3

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

Question 4

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

Answer 4

Gases
Petrol
Kerosene
Diesel oil 
Fuel oil 
Bitumen

Question 5

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

Answer 5

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

Question 6

What is fractional distillation

Answer 6

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.

Question 7

List how hydrocarbons in different fractions differ from each other

Answer 7

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.

Question 8

Explain a homologous series as a series of compound which…

Answer 8

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

Question 9

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

Answer 9

Carbon dioxide and water are produced

Energy is given out

Question 10

What is incomplete combustion

Answer 10

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.

Question 11

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

Answer 11

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

Question 12

How does carbon monoxide behave as a toxic gas

Answer 12

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.

Question 13

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

Answer 13

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

Question 14

What can impurities in some hydrocarbon fuels result in and why

Answer 14

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

Question 15

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

Answer 15

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.

Question 16

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

Answer 16

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. ????

Question 17

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

Answer 17

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

Question 18

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

Answer 18

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

Question 19

What does Cracking involve

Answer 19

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

Question 20

Why is cracking necessary

Answer 20

To match supply with demand

Question 21

What are the differences between alkAnes and alkEnes?

Answer 21

AlkAnes- Saturated, form a single bond C-C

AlkEnes- Unsaturated, form a double bond C=C

Question 22

Whats the equation for complete combustion

Answer 22

Hydrocarbon+Oxygen–> Carbon Dioxide + Water

Question 23

Whats the equation for incomplete combustion

Answer 23

Hydrocarbon+Oxygen—> Carbon monoxide+Carbon+Water

Question 24

What’s the general formula for AlkAnes

Answer 24

CnH2n+2

Question 25

What's the general formula for alkEnes

Answer 25

CnH2n

Question 26

What names are there for the number of Carbons.

Answer 26

``` Meth 1 Eth 2 Prop 3 But 4 Pent 5 Hex 6 ```

Question 27

In alkanes what does a longer chain mean

Answer 27

A higher boiling/melting point

Question 28

Can alkanes do addition reactions

Answer 28

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

Question 29

Can alkEnes react

Answer 29

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

Question 30

What happens when you react an alkAne with bromine water

Answer 30

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

Question 31

What happens when you react an alkEne with bromine water

Answer 31

The product is colourless

Question 32

What is cracking

Answer 32

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

Question 33

What can decane be cracked to for,

Answer 33

Octane and ethene

Question 34

Give an explanation of the practical using paraffin oil in cracking

Answer 34

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

Question 35

Why were first few bubbles of gas allowed to escape

Answer 35

They were just air from the boiling tube

Question 36

What does a catalyst do

Answer 36

Lower activation energy

Question 37

What is paraffin

Answer 37

Long hydrocarbon

Question 38

What happens when the heat is removed

Answer 38

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

Question 39

What are alcohols

Answer 39

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

Question 40

What is the functional group of alcohols

Answer 40

-OH

Question 41

What do all the names of alcohols end in

Answer 41

Anol

Question 42

What's the formula for ethanol

Answer 42

C2H5OH

Question 43

What are carboxylic acids

Answer 43

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

Question 44

How do we make carboxylic acids

Answer 44

Oxidising alcohols | Ethanol + oxygen- ethanoic acid + water

Question 45

What do smaller chains do

Answer 45

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

Question 46

What does a metal and an acid always produce

Answer 46

Hydrogen

Question 47

What are polymers

Answer 47

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

Question 48

What is a polymerisation reaction

Answer 48

Lots of monomers join up to make a polymer

Question 49

Give 3 examples of synthetic polymers

Answer 49

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

Question 50

Give 3 examples of natural polymers

Answer 50

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

Question 51

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

Answer 51

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

Question 52

What are the properties and uses of polyethene

Answer 52

Flexible cheap and good insulator | Used for plastic bags, bottles, cling film and polytunnels

Question 53

What are the properties and uses of polypropylene

Answer 53

Flexible does not shatter | Used for buckets, bowls, crates, ropes and carpets

Question 54

What are the properties and uses of polychloroethene (pvc)

Answer 54

Tough good insulator can be made hard or flexible | Used for window frames, gutters, pipes, insulation for electrical wires

Question 55

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

Answer 55

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

Question 56

How is poly(chloroethene) formed

Answer 56

Lots of chloroethene monomers joined up to make a long molecule

Question 57

What is condensation polymerisation

Answer 57

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.

Question 58

What does condensation polymerisation make

Answer 58

Water

Question 59

What happens when ethanol and ethanoic acid join

Answer 59

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

Question 60

What happens when ester bonds form

Answer 60

Water forms

Question 61

What parts of molecules join to form the water

Answer 61

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

Question 62

What do all esters contain

Answer 62

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

Question 63

What do you need to form a polyester

Answer 63

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

Question 64

What is most polymer waste

Answer 64

Non biodegradable

Question 65

Advantage and disadvantages of landfill

Answer 65

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

Question 66

Advantage and disadvantages of incineration

Answer 66

Produces useful energy But May produce harmful or toxic gases

Question 67

Advantage and disadvantages of recycling

Answer 67

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

Question 68

What forms when carboxylic acid monomers and alcohol monomers react together

Answer 68

Polyesters form