Fuels And Heats Of Reaction

Question 1

What are hydrocarbons?

Answer 1

Compounds consisting of hydrogen and carbon only, bonded together covalently

Question 2

Give an example of a hydrocarbon

Answer 2

CH4 - Methane

Question 3

What are the importance of hydrocarbons

Answer 3

Fuels for combustion

Question 4

Sources of hydrocarbons

Answer 4

Fossil fuels, crude oil, natural gas and coal

Question 5

Fossil fuels formed?

Answer 5

Remains of dead animals and plants

Question 6

Crude oil and natural gas formed?

Answer 6

Remains of marine animals and plants

Question 7

Methane formed

Answer 7

Digestive tracts [cattle] - greenhouse effect

Question 8

What are aliphatic hydrocarbons?

Answer 8

Straight and branched chains or rings of carbon atoms other than benzene ring

Question 9

Aromatic hydrocarbons

Answer 9

Benzene-type ring

Question 10

What is a homologous series?

Answer 10

It’s a family of organic compounds with the same general formula, similar chemical properties and successive members differing by CH2

Question 11

General formula for alkanes

Answer 11

CnH2n + 2

Question 12

What kinda bonds to alkanes have

Answer 12

Single bonds = saturated

Question 13

Physical properties of alkanes

Answer 13

Non- polar = insoluble in water but soluble in cyclohexane

Low boiling points = van der waal’s forces are easy to break

Question 14

What are isomers?

Answer 14

Compounds that have the same molecular formula but a different structural formula

Question 15

What kind of bonds to alkenes have?

Answer 15

Double bond = unsaturated

Question 16

What’s the general formula for alkenes?

Answer 16

CnH2n

Question 17

Physical properties of alkenes

Answer 17

Non polar

Low boiling point - the longer the chains the stronger the forces - higher boiling point

Question 18

What kind of bond in alkynes?

Answer 18

Triple bonds = unsaturated

Question 19

Physical properties of alkynes?

Answer 19

Low or zero polarity

Low boiling points

Question 20

What is dehydrocyclisation?

Answer 20

Involves converting chains into rings by removing 2H by heating in presence of suitable catalyst

Question 21

What is catalytic cracking?

Answer 21

Breaking long chains into shorter chains by heating in the absence of oxygen and presence of a catalyst
[some saturated some unsaturated]

Question 22

The products of catalytic cracking what are they used for?

Answer 22

Unsaturated - used as feedstock for polymer industry

Saturated - high octane, used for making petrol

Question 23

Advantages of catalytic cracking

Answer 23

Long chain compounds - converted into more useful compounds

Saturated and unsaturated

Question 24

Purpose of dehydrocyclisation in oil refining?

Answer 24

Increases octane number which reduces tendency of fuel to cause knocking

Question 25

What is hess's law?

Answer 25

Heat change of a reaction depends on the initial and final states or the reaction and is indecent of the route taken

Question 26

What is the name of the oil refining process?

Answer 26

Fractional distillation

Question 27

Identify the physical property that is the basis for hydrocarbons in oil refining being isolated as naphtha?

Answer 27

Boiling point

Question 28

What is oil refining?

Answer 28

When compounds in crude oil are separated according to different boiling points

Question 29

Give a major use for kerosene

Answer 29

Jet fuel

Question 30

Give a make use for residue

Answer 30

Road making

Question 31

Why are isomerisation and catalytic cracking desirable?

Answer 31

Increase octane number which reduces tendency of fuel to cause knocking

Question 32

Identify a property of a hydrocarbon that results in its presence in a particular fraction in oil refining

Answer 32

Boiling point

Question 33

Name the fraction in oil refining that is used for jet fuel

Answer 33

Kerosene

Question 34

What process is used to convert molecules in the fraction to smaller molecules that are in greater demand

Answer 34

Catalytic cracking

Question 35

What are the two reference hydrocarbons used to assign octane numbers to fuels?

Answer 35

Heptane and 2,2,4 tri-methylpentane

Question 36

Give two advantages of adding oxygenates?

Answer 36

Increases octane number which reduces knocking | And reduces pollution

Question 37

Give an example of an oxygenate

Answer 37

MTBE | Methyl tertiary- butyl ether

Question 38

Give two properties of hydrogen that makes it a fuel choice?

Answer 38

Low density | High octane number

Question 39

State one disadvantage of hydrogen as a fuel

Answer 39

Explosive

Question 40

Give two ways hydrogen gas is produced industrially

Answer 40

Electrolysis of water | Steam reforming of natural gases [ch4]

Question 41

Name two structural feature of hydrocarbons with high octane numbers

Answer 41

Short chains, branches

Question 42

What is the octane number?

Answer 42

Measure of the tendency of a fuel to cause knocking

Question 43

How can members of same homologous group differ in boiling point?

Answer 43

Smaller - fewer electrons and lower mr | Therefore weaker intermolecular forces

Question 44

Define heat of combustion

Answer 44

Heat change when one mole of a substance is burned completely in excess oxygen

Question 45

State the octane number of 2,2,4 trimethylpentane

Answer 45

100

Question 46

Explain why MTBE is sometimes added to fuel

Answer 46

Increases octane number and reduces pollution

Question 47

Name the substance previously added to motor fuel and why was it stopped

Answer 47

Tetraethyl lead - toxic [harmful for the environment] and also poisonous to catalytic converters

Question 48

What lab apparatuses is used to measure heats of combustion?

Answer 48

Bomb calorimeter

Question 49

Explain the term isomerisation

Answer 49

In presence of heat and suitable catalyst where structural formula is changed and hydrocarbons become branched

Question 50

How do you know one hydrocarbon has a higher octane number than the other?

Answer 50

Shorter chain and more branches = higher

Question 51

What is the nature of the chemicals that make up the bulk of crude oil?

Answer 51

Hydrocarbons

Question 52

Describe how crude oil is separated into useful substances in an oil refinery

Answer 52

Hot crude oil enters the base of column and is heated at the bottom Vapour moves up series of trays Depending on b.p High b.p - fractions come off at lower levels Low b.p - fractions come off at higher levels

Question 53

Major use for light gasoline and naphtha fractions of crude oil?

Answer 53

Petrol

Question 54

Why is catalytic cracking carried out in oil refining?

Answer 54

To give products with higher octane numbers

Question 55

Compounds Heptane and Methylbenzene are in the same fraction - which one? In oil refining

Answer 55

Naphtha

Question 56

Name two properties of compounds are responsible for compounds being found in same fraction in oil refining

Answer 56

Sim boiling point | Sim molecular mass

Question 57

What is auto ignition?

Answer 57

Ignition before spark is produced

Question 58

Name the three processes that are carried out in an oil refinery to modify the hydrocarbon structure and improve their octane number

Answer 58

1-isomerisation 2-dehydrocyclisation 3-catalytic cracking

Question 59

What are the six fractions in crude oil?

Answer 59

1. Refinery gas 2. Light gasoline [petrol] 3. Naptha 4. Kerosene 5. Gas oil 6. Residue [RED PONIES NEVER KICK GOOD RIDERS]

Question 60

Give a use of refinery gas

Answer 60

Domestic heating gas

Question 61

Give a use of light gasoline

Answer 61

Motor fuel

Question 62

Give a use of Naphtha

Answer 62

Solvents

Question 63

Give a use of kerosene

Answer 63

Aviation fuel

Question 64

Give a use for gas oil

Answer 64

Diesel

Question 65

Give a use for residue

Answer 65

Bitumen, lubricating oil

Question 66

How is hydrogen as a fuel produced and give an equation

Answer 66

Steam reforming of methane | CH4 + H20 = CO + 3H2

Question 67

Why are mercaptans added to natural gas?

Answer 67

For detection because they are odourless

Question 68

What are mercaptans

Answer 68

Sulfur compounds added to LPG and Natural has for detection because they are odourless

Question 69

What instrument is used to measure heat of combustion

Answer 69

Bomb calorimeter

Question 70

Two components liquified as LPG

Answer 70

Propane | Butane

Question 71

What is heat of reaction?

Answer 71

It’s the heat change in KJ/mol as a reaction proceeds according to a balanced chemical equation

Question 72

What is the principal use made of oxygenates such as MTBE in the petrochemicals industry?

Answer 72

Raise octane number which prevents auto-ignition

Question 73

Smoke Petrol Engine

Answer 73

Induction - Petrol vaporised + drawn with air into a cylinder as piston moves down Compression - then compressed as piston moves back up and causes temp to rise Ignition - petrol/air mixture is ignited by spark and resulting explosion pushes piston back down to supply energy to propel car Exhaust - Waste are pushed out as piston rises back up cylinder