Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

LC Chemistry > Chapter 21 - Fuels & Heats of Reactions > Flashcards

Chapter 21 - Fuels & Heats of Reactions Flashcards

You may prefer our related Brainscape-certified flashcards:
Periodic Table flashcards Chemistry 101 flashcards AP® Chemistry flashcards Organic Chemistry 101 flashcards
1
Q

Organic chemistry

A

The study of the compounds of carbon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Hydrocarbon

A

A compound that only contains hydrogen and carbon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Name common sources of hydrocarbons

A

Coal, natural gas (methane) & petroleum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Fossil fuels

A

Fuels that were formed from the remains of plants and animals that lived millions of years ago

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the three main types of hydrocarbons?

A

alkanes

alkenes

alkynes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Give the characteristics of alkanes

A

○ All atoms are linked together by single bonds

○ Names all end in -ane

○ All prepared in the same way

○ All have similar chemical properties

○ First four are gases, next twelve are liquids, rest are waxy solids

○ Are saturated compounds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Saturated compound

A

One in which there are only single bonds between atoms in a molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the general formula for alkanes?

A

CₙH₂ₙ₊ₙ

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Homologous series

A

Defined as:

  • a series of compounds of similar chemical properties
  • showing gradations in physical properties
  • having a general formula for its members
  • each member having a similar method of preparation
  • each member differing from the previous member by a CH₂ unit
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Structural isomers

A

Compounds with the same molecular formula but different structural formulas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How do you name an Alkane?

A
  1. Identify the longest chain of carbon atoms
  2. Identify the functional group
  3. Number the carbon chain starting from the end that gives the substituents the lowest possible number
  4. Indicate the type and position of substituents, and if multiples exist we use prefixes like di, tri etc
  5. Name all substituents in alphabetical order
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Give the characteristics of alkenes

A
  • Contain at least one double carbon bond in a chain
  • Are unsaturated
  • Names end in ene
  • First three are gases, next eleven are liquids, rest are waxy solids
  • Boiling points increase as you go down the series
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Unsaturated compound

A

One that contains one or more double or triple bonds between the atoms in the molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the general formula for alkenes?

A

CₙH₂ₙ

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How do you name an alkene?

A
  1. Identify the longest chain of carbon atoms containing the c=c bond
  2. Identify the functional group
  3. Number the carbon chain starting from the end that is closest to the c=c bond
  4. Indicate the type and position of substituents, and if multiples exist we use prefixes like di, tri etc
  5. Name all substituents in alphabetical order
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Explain how to prepare ethene

A
  1. Pour ethanol into a boiling tube and add glass wool
  2. Place a small piece of aluminium oxide (Al₂O₃) half way
  3. Gently heat
  4. Discard first tube and collect five more
  5. Lift tubing from water and turn off bunsen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What happens when the aluminium oxide (Al₂O₃) is heated during the preparation of ethene experiment?

A
  • Bubbles of gas collect in the gas tube
  • Aluminium oxide (Al₂O₃) becomes hot, heat reaches the ethanol which changes to vapour, passes over the hot aluminium oxide (Al₂O₃) and is dehydrated to form ethene
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Why is the tubing lifted from the water at the end of the preparation of ethene experiment?

A

To prevent suck back → as air in the boiling tube cools, a vacuum is created and water is sucked vack to fill the space. The cold water could cause the hot glass to crack and break

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the physical properties of ethene?

A
  • Colourless gas
  • Sweetish smell
  • Insoluble in water
  • Soluble in cyclohexane
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Ethene burns with a…

A

…yellow luminous flame and is slightly smokey

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Give the equation for the combustion of ethene in oxygen

A

C₂H₄ + 3O₂ → 2CO₂ + 2H₂O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is observed when bromine water is added to a tube of ethene gas?

A

The colour changes from orange to colourless

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is observed when acifified potassium permanganate (KMnO4) is added to a tube of ethene gas?

A

Colour changes from purple to colourless

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Give a use for ethene

A

Fruits produce ethene naturally to help them ripen.

Also used to make plastic e.g polythene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Give the characteristics of alkynes

A
  • Contain a triple carbon carbon bond
  • Are highly unsatutated
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the general formula for alkynes?

A

CnH2n-2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is ethyne used for?

A

Oxyacetylene welding and cutting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the equation for the preparation of ethyne?

A

CaC2 + 2H2O → Ca(OH)2 + C2H2

calcium carbide + water → calcium hydrocarbide + ethyne gas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Explain how to prepare ethyne

A
  1. Add a small amount of calcium carbide into a buchner flask using a spatula
  2. Set up apparatus so that the gas produced passes through acidified copper (II) sulfate (CuSO4) solution to remove impuritied
  3. Slowly add water to flask to get a steady and slow production of ethyne
  4. Collect a few tubes of the gas
  5. Do not pour down the drain
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What impurities does calcium carbide contain, and what impurities does it cause ethyne to contain?

A

calcium sulfide

calcium phosphide

calcium nitride

hydrogen sulfide (H2S)

phosphine (PH3)

ammonia (NH3)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Is the reaction of calcium carbide and water in the production of ethyne exothermic or endothermic?

A

exothermic → the flask becomes warm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What are the physical properties of ethyne?

A
  • Colourless gas
  • Sweet smell
  • Insoluble in water, but dissolves in organic compounds like propanone and cyclohexane
  • Stored in steel containers as it is very explosive
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Ethyne burns with a…

A

…luminous smoky flame and a lot of soot is produced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Give the equation for the combustion of ethyne in oxygen

A

2C2H2 + 5O2 → 4CO2 + 2H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is observed when bromine water is added to a test tube of ethyne?

A

Colour changes from orange to colourless. This is evidence of unsatutation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What is observed when acifified potassium permanganate (KMnO4) is added to a tube of ethyne gas?

A

Colour changes from purple to colourless

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Aliphatic compound

A

Organic compound that consists of open chains of carbon atoms and closed chain compounds (rings) that resemble them in chemical properties

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Aromatic compounds

A

Compounds that contain a benzene ring in their structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Give the characteristics of benzene

A
  • Is highly unsaturated
  • Is very unreactive
  • All bond lengths are the same
  • Each carbon has one electron which belongs to the whole molecule, which gives it extra stability
  • Molecule is flat and all bond angles are 109.5°
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What is the traditional name for methylbenzene?

A

toluene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Give the characteristics of methylbenzene

A
  • Liquid at room temperature
  • Is insoluble in water as it is non-polar and water is polar
  • Iodine is soluble in methylbenzene but not water, as it is also non-polar
42
Q

How are fossil fuels formed?

A

Layers of silt and mud covered bodies of dead sea creatures millions of years ago. Over the years the decay and pressure turned these bodies into oil and gas

43
Q

Describe the appearance of crude oil

A

Thick black liquid that doesn’t burn easily and has an unpleasant odour

44
Q

Fractional distillation

A

This is the heating of the crude oil and separating out of the different mixtures on the basis of their boiling points

45
Q

Outline the process of fractional distillation

A
  1. Crude oil heated to ≈600°C
  2. Oil enters column partially vapourised
  3. Trays have holes called bubble caps
  4. Temperature drops as you move up the tower
  5. Substances with high boiling points (large hydrocarbons) come off as liquids at the bottom
  6. Substances with low boiling points (small hydrocarbons) come off as gases at the top
  7. Collected in trays, which are connected to an outlet from which the fraction is collected
46
Q

List the fractions of crude oil from top to bottom

A
  1. Refinery gas (petroleum gas/LPG)
  2. Petrol gas (light gasoline)
  3. Naphtha
  4. Kerosene (paraffin)
  5. Diesel oil (gas oil)
  6. Lubricating oil
  7. Fuel oil
  8. Bitumen
47
Q

What is refinery gas used for?

A

Bottled gas (propanone/butane)

48
Q

What is petrol used for?

A

Fuel for car engines

49
Q

What is naphtha used for?

A

Solvents and used in the petrochemical industry

50
Q

What is kerosene (paraffin) used for?

A

Fuel for aircraft and stoves

51
Q

What is diesel oil (gas oil) used for?

A

Fuel for road vehicles and trains

52
Q

What is lubricating oil used for?

A

Lubricant for engines and machines, waxes and polishes

53
Q

What is fuel oil used for?

A

Fuel for heating ships, power stations and heating plants

54
Q

What is bitumen used for?

A

Road surfacing and roofing

55
Q

Name the compounds added to refinery gas

A

It is odourless so compounds containing sulphur called mercaptans are added to give the characteristic smell so leaks can be detected

56
Q

Lubricating oil, fuel oil and bitumen are called…

A

…residue fractions

57
Q

How do engines work?

A
  1. In the internal combustion engine, a mixture of petrol and air is drawn into the cylinder
  2. Mixture is compressed and ignited by a spark
  3. The gases produced by the explosion drives the piston down
  4. This rotates the crankshaft causing the wheels to turn
58
Q

Knocking

A

If the explosion in the engine occurs too early, it causes the pistons to vibrate and a metallic noise can be heard from the engine. This noise is called knocking. The early explosion is called by the petrol-air mixture exploding when being compressed rather than exploding due to the spark

59
Q

Auto-ignition

A

Premature ignition (explosion) of the petrol-air mixture before normal ignition of the mixture by a spark takes place

60
Q

Octane number

A

The octane number of a fuel is a measure of the tendency of the fuel to resist knocking

61
Q

Name the reference hydrocarbons, give their octane numbers and the tendency they have to auto-ignite

A

2,2,4-trimethylpentane (iso-octane), very efficient, low tendency to auto-ignite, 100

heptane, very inefficient, prone to auto-ignition, 0

62
Q

What are the factors affecting octane numbers?

A
  1. Length of chain - shorter the alkane chain, the higher the octane number
  2. Degree of branching - the more branched the chain the higher the octane number
  3. Straight chain vs cyclic structures - cyclic compounds have higher octane numbers than straight-chain compounds
63
Q

What anti-knocking additive was added to fuel in the 1920s? What problems were associated with this additive?

A

Discovered a small amount of lead reduced knocking, e.g tetraethyl lead Pb(C2H5)4

But lead can damage health and catalytic converter in the car so it was removed from petrol

64
Q

What are four ways to increase the octane numbers of fuels?

A
  1. Isomerisation
  2. Catalytic cracking
  3. Reforming / Dehydrocyclisation
  4. Adding oxygenates
65
Q

What is isomerisation?

A

Changing straight chained molecules into their branched equivalents

66
Q

Explain the process of isomerisation

A
  1. The alkanes are heated in the presence of a suitable catalyst to break the chains apart
  2. Then they join back together again, when the product is more likely to be branched
  3. Any straight chains left are removed and sent over the catalyst again
67
Q

Catalytic cracking

A

The breaking down of long-chain hydrocarbon molecules by the action of heat and catalysts into short chain molecules for which there is a greater demand

68
Q

Give two benefits of catalytic cracking

A
  • The short chain molecules produced in catalytic cracking tend to be highly branched, thus petrol containing them have a higher octane number
  • The alkanes produced are important as feedstock for the petrochemical industry
69
Q

What is reforming/dehydrocyclisation?

A

Using catalysts to form ring compounds, which have high octane numbers

70
Q

Why is the addition of benzene to fuel strictly controlled?

A

Benzene is a carcinogen

71
Q

Oxygenate

A

Name used by petroleum chemists to refer to any fuel containing oxygen in its molecules

72
Q

What are the three main molecules containing oxygen that are added to petrol?

A

methanol

ethanol

MTBE (methyl tertiary butyl ether / 2-methoxy-2-methylpropane)

73
Q

Why are oxygenates added to fuel?

A
  • To increase the octane number of the fuel
  • They give rise to very little pollution when burned
74
Q

Why does the composition of fuel vary from season to season?

A

In winter, the fuel is more volatile (low boiling point) and in summer it is less volatile

75
Q

What are the two main methods of producing hydrogen?

A

Steam reforming of natural gas

Electrolysis of water

76
Q

Explain steam reforming of natural gas and give an equation

A

Methane is reacted with steam and a suitable catalyst

CH4 + H2O → 3H2 + CO

77
Q

Give an equation for the electrolysis of water

A

H2O → H2 + ½O2

78
Q

What is the most important use of hydrogen?

A

The manufacture of ammonia

3H2 + N2 → 2NH3

79
Q

Give one advantage and one disadvantage of using hydrogen as a fuel

A

✔ It is environmentally friendly as the only by-product is water

✘ It can form an explosive mixture with air so it has to be stored and transported carefully

80
Q

Thermochemistry

A

The study of heat changes

81
Q

Exothermic

A

A reaction in which heat is liberated eg fuel burning

82
Q

Endothermic

A

A reaction in which heat is taken in e.g amminium nitrate + ammonium chloride

83
Q

Heat of reaction

A

The heat change that occurs when the number of moles of reactants indicated in the balanced equation for a reaction react completely

84
Q

What is ΔH used to indicate?

A

It is used to indicate the heat change taking place when a chemical reaction occurs.

ΔH is negative if their is a heat loss in the system i.e exothermic

ΔH is positive is there is a heat gain in the system i.e endothermic

85
Q

What are the rules for writing a thermochemical equation?

A
  • The equation must be balanced
  • Although the SI unit for energy is the joule, this is too small so we use the kJ
  • If the moles in the equation changes, so too will the ΔH
  • The physical states of the reactants and products is always given
  • Reaction carried out at 25­°
86
Q

Heat of combustion

A

The heat change that occurs when one mole of a substance is completely burned in excess of oxygen

87
Q

What tool is used to accurately measure heat of combustion?

A

Bomb calorimeter

88
Q

How does a bomb calorimeter work?

A
  1. A fixed amount of the sample whose heat of combustion is to be measured is placed in a cucible inside the bomb
  2. Bomb is placed in a container of a known quantity of water
  3. Oxygen is pumped in excess/under pressure into the bomb
  4. Electric wires ignite the sample
  5. Rise in water temperature is recorded
  6. The calculation of m x c x Δt works out the heat of combustion of the sample
89
Q

Kilogram calorific value

A

The kilogram calorific value of a fuel is the heat energy produced when 1kg of fuel is completely burned in oxygen

90
Q

Bond energy

A

The average energy required to break one mole of a particular covalent bond and to separate the neutral atoms completely from each other

91
Q

Heat of neutralisation

A

The heat change observed when one mile of H+ ions from an acid reacts with one mole of OH- ions from a base

92
Q

What is the measure/unit for heat of neutralisation?

A

kJ mol-1

93
Q

What is the average ΔH for the reaction of all strong acids with all stong bases?

A

-55 → -58 kJ mol-1

94
Q

Outline the experiment to determine the heat of reaction of HCl with sodium hydroxide

A
  1. Place a known volume of HCl into a polystyrene cup
  2. Same volume of sodium hydroxide is placed in a second cup
  3. The volumes and concentrations are recorded
  4. Both solutions are allowed to stand until they are at the same temperature
  5. Record temperature
  6. Quickly add the NaOH solution to the HCl solution, taking care not to spill
  7. Immediately put lid on cup
  8. Stir continuously
  9. Record the max temperature
95
Q

Is the reaction of NaOH and HCl endo or exothermic?

A

Exothermic (-)

96
Q

Specific heat capacity

A

The amount of heat required to raise the temperature of 1kg of a substance by 1K (J kg-1 K-1)

97
Q

What assumptions are made in the experiment to determine the heat of reaction of HCl with NaOH?

A
  • We assume the plastic absorbs no heat
  • We assume the acid and base have the same specific heat capacity as water (i.e 4060 J kg-1 K-1)
  • We assume the density of the solution is the same as water (i.e 100cm3 of solution has a mass of 100g/0.1kg)
98
Q

Heat of formation

A

The heat change that takes place when one mole of compound in its standard state is formed from its elements in their standard state

99
Q

Standard state

A

A compound’s natural form at 25°C and at atmospheric pressure of 101 kPa

100
Q

Hess’s Law

A

If a chemical reaction takes place in a number of stages, the sum of the heat changes in the separate stages is equal to the heat change if the reaction is carried out in one stage

101
Q

Law of Conservation of Energy

A

Energy cannot be created or destroyed, but can only be converted from one form to another

LC Chemistry (24 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions