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Flashcards in Fuels And Heats Of Reaction Deck (73):
1

What are hydrocarbons?

Compounds consisting of hydrogen and carbon only, bonded together covalently

2

Give an example of a hydrocarbon

CH4 - Methane

3

What are the importance of hydrocarbons

Fuels for combustion

4

Sources of hydrocarbons

Fossil fuels, crude oil, natural gas and coal

5

Fossil fuels formed?

Remains of dead animals and plants

6

Crude oil and natural gas formed?

Remains of marine animals and plants

7

Methane formed

Digestive tracts [cattle] - greenhouse effect

8

What are aliphatic hydrocarbons?

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

9

Aromatic hydrocarbons

Benzene-type ring

10

What is a homologous series?

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

11

General formula for alkanes

CnH2n + 2

12

What kinda bonds to alkanes have

Single bonds = saturated

13

Physical properties of alkanes

Non- polar = insoluble in water but soluble in cyclohexane
Low boiling points = van der waal's forces are easy to break

14

What are isomers?

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

15

What kind of bonds to alkenes have?

Double bond = unsaturated

16

What's the general formula for alkenes?

CnH2n

17

Physical properties of alkenes

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

18

What kind of bond in alkynes?

Triple bonds = unsaturated

19

Physical properties of alkynes?

Low or zero polarity
Low boiling points

20

What is dehydrocyclisation?

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

21

What is catalytic cracking?

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

22

The products of catalytic cracking what are they used for?

Unsaturated - used as feedstock for polymer industry
Saturated - high octane, used for making petrol

23

Advantages of catalytic cracking

Long chain compounds - converted into more useful compounds
Saturated and unsaturated

24

Purpose of dehydrocyclisation in oil refining?

Increases octane number which reduces tendency of fuel to cause knocking

25

What is hess's law?

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

26

What is the name of the oil refining process?

Fractional distillation

27

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

Boiling point

28

What is oil refining?

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

29

Give a major use for kerosene

Jet fuel

30

Give a make use for residue

Road making

31

Why are isomerisation and catalytic cracking desirable?

Increase octane number which reduces tendency of fuel to cause knocking

32

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

Boiling point

33

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

Kerosene

34

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

Catalytic cracking

35

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

Heptane and 2,2,4 tri-methylpentane

36

Give two advantages of adding oxygenates?

Increases octane number which reduces knocking
And reduces pollution

37

Give an example of an oxygenate

MTBE
Methyl tertiary- butyl ether

38

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

Low density
High octane number

39

State one disadvantage of hydrogen as a fuel

Explosive

40

Give two ways hydrogen gas is produced industrially

Electrolysis of water
Steam reforming of natural gases [ch4]

41

Name two structural feature of hydrocarbons with high octane numbers

Short chains, branches

42

What is the octane number?

Measure of the tendency of a fuel to cause knocking

43

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

Smaller - fewer electrons and lower mr
Therefore weaker intermolecular forces

44

Define heat of combustion

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

45

State the octane number of 2,2,4 trimethylpentane

100

46

Explain why MTBE is sometimes added to fuel

Increases octane number and reduces pollution

47

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

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

48

What lab apparatuses is used to measure heats of combustion?

Bomb calorimeter

49

Explain the term isomerisation

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

50

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

Shorter chain and more branches = higher

51

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

Hydrocarbons

52

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

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

53

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

Petrol

54

Why is catalytic cracking carried out in oil refining?

To give products with higher octane numbers

55

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

Naphtha

56

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

Sim boiling point
Sim molecular mass

57

What is auto ignition?

Ignition before spark is produced

58

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

1-isomerisation
2-dehydrocyclisation
3-catalytic cracking

59

What are the six fractions in crude oil?

1. Refinery gas
2.Light gasoline [petrol]
3.Naptha
4.Kerosene
5.Gas oil
6.Residue

[RED PONIES NEVER KICK GOOD RIDERS]

60

Give a use of refinery gas

Domestic heating gas

61

Give a use of light gasoline

Motor fuel

62

Give a use of Naphtha

Solvents

63

Give a use of kerosene

Aviation fuel

64

Give a use for gas oil

Diesel

65

Give a use for residue

Bitumen, lubricating oil

66

How is hydrogen as a fuel produced and give an equation

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

67

Why are mercaptans added to natural gas?

For detection because they are odourless

68

What are mercaptans

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

69

What instrument is used to measure heat of combustion

Bomb calorimeter

70

Two components liquified as LPG

Propane
Butane

71

What is heat of reaction?

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

72

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

Raise octane number which prevents auto-ignition

73

Smoke Petrol Engine

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