Brainscape's Knowledge GenomeTM

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


See full index

LC Chemistry > Fuels and Heats of reaction > Flashcards

Fuels and Heats of reaction Flashcards

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

Hydrocarbon

A

A compound that contains only carbon and hydrogen

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

Saturated compound

A

a compound in which there are only single bonds between the atoms in the molecule

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

Unsaturated compound

A

One which contains at least one double or triple bonds netweem the atoms in the molecule

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

Structural isomers

A

Compounds with the same molecular formula but different structural formulae

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

Aliphatic (compound)

A

An organic compound that consists of straight (open) chains of carbon atoms and closed chain compounds with similar properties

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

Aromatic (compound)

A

An organic compound that contains a benzene ring structure in their molecules

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

Octane Number

A

Octane number of a fuel is a measure of the tendency of the fuel to resist knocking

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

Catalytic cracking

A

The breaking down of long chain hydro-carbon molecules into short chain molecules by heat and catalysts

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

Auto-ignition

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Alkanes

A

These compounds are a family of hydrocarbons in which all atoms are linked by single bonds (saturated compounds)

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

Alkanes - formula

A

Cₙ H₂ₙ₊₂

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Order

A 
Meth
Eth
Prop
But
Pent
Hex
Hept
Oct
Non
Dec
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Alkane structual and condensed formulas

A

on hardback

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

Alkenes - formula

A

Cₙ H₂ₙ

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

Alkenes

A
  1. A homologous series of aliphatic hydrocarbons
  2. Lowest member of the series is ethene (2 carbon atoms)
  3. Each alkene molecule contains a carbon-carbon double bond
  4. Unsaturated compounds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Alkenes - methene

A

No methene due to double bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Alkynes endings

A

ends in -yne

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Alkynes

A

Contain a carbon-carbon triple bond

Highly unsatured

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

Alkynes formula

A

Cₙ H₂ₙ₋₂

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Ethyne

A

Name - Ethyne
Formula - C₂ H₂
Structural formula: H - C = C - H

Ethyne is the first of the series as you must have a carbon-carbon triple bond. (You need at least 2 carbons)

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

Endothermic reaction

A

Energy + reactants –> products

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

Activation energy

A

Activation energy is the maximum point on the reaction graph

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

Example of exothermic reaction and endothermic reaction

A

Exothermic reaction: Hydrochloric acid + magnesium

Endothermic reaction: water + ammonium nitrate

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

Bomb calorimeter

  • use
  • method
A

Used to find accurate values for heats of combustion

  • Sample is ignited using electrically heated wire
  • Excess oxygen ensures complete combustion of sample
  • Heat produced by rapid + complete combustion of the sample heats, water + temperature is recorded
  • Apparatus is well insulated to prevent heat loss
  • Amount of heat used to start burning can be calculated and removed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Bond energy

A
  • Average C-H bond energy in methane: 412 kJ mol⁻¹ ie. E(C-H) = 412 kJ mol⁻¹
  • Energy of a particular bond can vary
  • It is unusual to quote the average bond energies
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Natural gas

A
  • A colourless, odourless mixture of gases made up mostly of methane (CH₄). Other gases that can form part of natural gas include small amounts of ethane (C₂ H₆), propane (C₃ H₈), and butane (C₄ H₁₀)
  • Methane burns relatively cleanly to produce heat energy + by-products of water and carbon dioxide
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Why is natural gas useful?

A
  • high kg calorific value
  • Plentiful
  • Easily distributed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Why mercaptans are added to natural gas

A

Due to natural gas being highly inflammable + explosive, mercaptans are added so it can be detected

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

Fractional distillation

A

A large-scale, continuous process which separates crude oil into a number of useful mixtures called fractions
eg. refinery gas is a fraction that can be used as a domestic gas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Octane number

A

Measure of the tendency of the fuel to resist knocking
eg. 2, 2, 4 - trimethlypentane is assigned an octane number of 100
heptane is assigned an octane number of 0

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

Factors affecting octane numbers

A

The shorter the alkane chain, the more branched the chain, and cyclic compounds all lead to higher octane numbers

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

Methods used to increase the octane number of petrol

A
  • Isomerisation
  • Catalytic cracking
  • Dehydrocyclisation
  • Adding oxygenates
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Ways of manufacturing hydrogen

A
  • steam reforming of natural gas

- electrolysis of water

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

Isomerisation

A

involves changing straight-chained hydrocarbons into branched-chained isomers. The branched-chained isomers burn more smoothly, therefore have higher octane number.

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

Catalytic cracking

A

involves breaking down long chained hydrocarbons (low demand) into short chained molecules (high demand). Short-chained hydrocarbonsa higher octane number + tend to be highly branched.

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

Dehydrocyclisation

A

involves conversion of straight chained hydrocarbons to form ring compounds. Then converted into aromatic compounds. Done in presence of a catalyst. As hydrogen is a byproduct of this reaction it is called ‘dehydro’. Aromatic compounds have high octane number but also carcinogenic.

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

Adding oxygenates

A

the addition of oxygen compounds to the petrol.

Tend to be of two types (a) addition of alcohols i.e. methanol (octane no. of 114) and (b) addition of ethers i.e. methyl tert-butyl ether (MTBE) (octane no. of 118).

These compounds (a) increase octane number of the petrol (b) cause less pollution as they reduce level of carbon monoxide in exhaust fumes.

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

Catalytic cracking allows what?

A

Allows large hydrocarbon molecules to be broken down into smaller, more useful hydrocarbon molecules

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

Catalytic cracking method

A

Fractions containing large hydrocarbon molecules are vaporised + passed over a hot catalyst. This breaks chemical bonds in the molecules + forms smaller hydrocarbon molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Why do catalytic cracking

A

Fuels made from oil mixtures w/ large hydrocarbon molecules -> not efficient, do not flow easily, difficult to ignite

Crude oil –> often too many large hydrocarbon molecules + not enoughh small hydrocarbon molecules to meet demand

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

Heat of neutralisation

A
  • Nearly always exothermic (-△H)
  • Measured in kJ/mol or kJ mol⁻¹
  • Always less than -57 kJ mol⁻¹

WRITE A NEGATIVE IN FRONT OF THE ANSWER IF ASKED TO CALCULATE HEAT OF NEUTRALISATION

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

How to find out if substance is acid or base

A

Acid: contains H⁺ ions eg. HCl

Base: Contains OH eg. NaOH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Calculating the heat liberated in a reaction

A

Heat liberated/given out = mass x specific heat capacity x rise in temperature

(m x c x (t₂ - t₁)

mass - kg
shc - J kg⁻¹ K⁻¹

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Mercaptans

A

Chemicals added to odourless gases to give them an unpleasant smell so that gas leaks can be detected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Who discovered benzene?

A

Michael Faraday in 1825

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Properties of benzene

A

Formula: C₆ H₆
Highly unsaturated
Highly toxic
Carcinogenic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Points about benzene that puzzled chemists

A
  1. Reactivity

2. Bond lengths

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q
  1. Reactivity of Benzene
A

Predicted benzene could be highly reactive. Found to be very unreactive.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q
  1. Bond lengths of Benzene
A

Problems about alternating double + single bonds between the carbon atoms. When bond lengths measured, was found that all carbon-carbon bond lengths were same. Single bond is longer than double bond. Bond lengths in benzene are intermediate between that of a single bond + double bond.

50
Q

Why benzene is unreactive

A

The electrons were delocalised.

Delocalisation of electrons gives the benzene molecule extra stability + accounts for its unreactivity

51
Q

Angles on benzene molecule

A

The molecule is a flat molecule with all bond angles equal to 120°

52
Q

Examples of aromatic hydrocarbons

A

Methylbenzene

Ethylbenzene

53
Q

Methylbenzene properties

A
  • Liquid at room temp
  • Insoluble at water
  • Will dissolve in organic solvents such as cyclohexane and propanone
  • A good organic solvent
54
Q

Fractional distillation - residue

A

bitumen for roads + roofing

55
Q

Fractional distillation - fuel oils

A

fuels for ships, factories, central heating

56
Q

Fractional distillation - Lubricating oil

A

lubricating oils, waxes, polishes

57
Q

Fractional distillation - diesel oils

A

diesel fuels

58
Q

Fractional distillation - kerosene (paraffin oil)

A

jet fuel, paraffin for lighting + heating

59
Q

Fractional distillation - petrol (gasoline)

A

petrol for vehicles

60
Q

Fractional distillation - naphta

A

chemicals

61
Q

Fractional distillation - gases

A

liquefied petroleum gas

62
Q

environmental effect of the release of methane

A

greenhouse effect

63
Q

source of methane

A

flatulence of cows

64
Q

why lead was removed from petrol

A

lead is toxic to humans

65
Q

additives to increase octane number

A
  • addition of alcohol: methane

- addition of ethers (methyl tert-butyl ether

66
Q

additives used to increase octane number of a fuel

A
  • Methanol / ethanol

- Methyl-tert-butyl-ether

67
Q

How fractional distillation is carried out

A
  • know diagram
  • hot crude oil introduced at base of fractionating column
  • vapur moves up through a series of trays
  • fractions come off through outlets depending on their boiling points
  • temp gradient shown, highest temp at bottom
68
Q

something undergoing dehydrocyclisation diagram

A

literally just becomes a circle thing with the c forming the circle

eg. hexane -> cyclohexane + hydrogen

69
Q

heat produced by a reaction

A

heat = mcΔΘ

70
Q

heat of reaction

A

the heat change when the numbers of moles of reactants indicated in the balanced equation for the reaction react completely

71
Q

heat of combustion

A

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

72
Q

kilogram calorific value

A

of a fuel is the heat energy produced when 1kg of the fuel is completely burned in oxygen

73
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

74
Q

heat of neutralisation

A

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

75
Q

heat given out

A

c(t₂ - t₁)

76
Q

heat of formation

A

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

77
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

78
Q

Law of conservation of energy

A

energy cannot be created or destroyed, but can only be converted from one form of energy into another

79
Q

calculating heat of combustion

A

ΔH° (combustion) = ΣΔH 𝒻(Products) - ΣΔH 𝒻(Reactants)

measured in kJ mol⁻¹ !!!!

(div by the no. of moles to get it to 1 mole)

80
Q

fractionation of crude oil

A

separation into components according to molecular size by distillation

81
Q

components of liquid petroleum gas (LPG)

A

propane

butane

82
Q

calculating heat of reaction (/when one mole of each solution is used)

A

use mcΔΘ

then div by no. of moles if u need to get it in terms of 1 mole

83
Q

effect of length of carbon chain on boiling point

A

the longer the carbon chain (more carbon atoms), the higher the boiling point

84
Q

hydrocarbon gas produced by anaerobic bacterial decomposition of either animal waste or vegetation

A

methane (CH₄)

85
Q

uses of methane

A

fuel
steam reforming
production of fertilizer

86
Q

why is the concentration of gas in the atmosphere a cause of concern?

A

global warming

enhanced greenhouse gas

87
Q

Why do high molecular mass alkanes have high boiling points?

A

stronger intermolecular bonds

88
Q

the physical property that is the basis for hydrocarbons being isolated in the process of fractional distillation

A

boiling point

relative molecular mass

89
Q

the two reference hydrocarbons used to assign octane numbers to fuels

A

heptane and 2,2,4-trimethylpentane

90
Q

2 advantages of adding oxygenates to fuel

A
  • increase octane number, reduces knocking

- reduces pollution

91
Q

two properties of hydrogen that made it the fuel choice for the space shuttle

A
  • low density
  • high kilogram calorific value
  • minimally pollution (only product of combustion is water)
92
Q

disadvantage of hydrogen as a fuel

A
  • leaks easily out of containers
  • explosive
  • hazardous
  • expensive
93
Q

two ways hydrogen gas is produced industrially

A
  • steam reforming of natural gas
  • dehydrocyclisation
  • electrolysis of water
94
Q

balanced equations for combustion of something in oxygen

A

reactants: itself + O2
products: co2 and h2o

95
Q

exothermic reaction profile graph

A

know what the graph looks like and how to label

96
Q

fractions which contain molecules with the carbon chain lengths needed for petrol

A
  • light gasoline/petroleum

- naphtha

97
Q

two changes to the hydrocarbon molecule during dehydrocyclisation

A
  • removal of hydrogen

- ring formation

98
Q

what is the principal use made of oxygenates such as methyl tert-butyl ether, MTBE, in the petrochemicals industry?

A
  • raise octane number
  • prevent auto-ignition
  • cleaner emissions
99
Q

in which fraction of crude oil do pentane and its isomers occur?

A

light gasoline/petrol

100
Q

how do molecules of naphtha differ from molecules of the gas oil fraction?

A
  • have shorter chains

- gas oils have longer chains

101
Q

fractional distillation separation

A

know the order, where each of the fractions end up

naphtha condenses higher up while gas oil comes off lower down

102
Q

uses for catalytic cracking

A
  • give useful products

- gives higher octane numbers

103
Q

why is the use of benzene in petrol strictly controlled?

A

benzene is carcinogenic/toxic

104
Q

two reasons why the addition of lead to petrol has been discontinued

A
  • it poisons/destroys the catalyst in catalytic converter

- lead emission presents a health hazard (toxic to living things)

105
Q

why methane is useful/excellent as a fuel

A
  • high kilogram calorific value
  • clean (burns to produce carbon dioxide and water)
  • plentiful
  • non-toxic
106
Q

what does LPG stand for?

A

Liquefied petroleum gas

107
Q

source from which methane is released to the atmosphere

A
  • fossil fuels
  • flatulence of cows
  • slurry
  • anaerobic decay
  • coal(coal gas, coal mines)
108
Q

why it is possible to measure experimentally the heat of formation of co2 and water but not that of ethanoic acid

A

ethanoic acid cannot be formed directly from elements
/
formation of ethanoic acid is not a combustion reaction

109
Q

components of air feedstock that are removed prior to fractional distillation/before it is liquefied

A
  • water vapour
  • carbon dioxide
  • dust
  • oil particles
110
Q

how the air intake is liquefied prior to fractional distillation

A
  • cooled

- compressed (placed under pressure)

111
Q

boiling points of the fractions

A

Top - lower boiling points

Bottom - higher boiling points

112
Q

which of the fractional distillation products is oxygen?

A

the bottom

113
Q

uses for the oxygen gas produced by the fractionation of liquid air

A
  • steel-making
  • breathing aid
  • rocket fuel
  • beauty treatment
  • using bomb calorimeter for measuring heats of combustion
  • medical treatment (eg. muscle injury)
114
Q

fractional distillation of pure liquid air process

A

-diagram

  • compressed air warms up in column
  • oxygen collects at base of column + removed
  • nitrogen at top of column
115
Q

industrial use for hydrogen produced in dehydrocyclisation

A

hydrogenation (of vegetable oils) / fuel / preparation of hydrochloric acid/ammonia

116
Q

suggest a reason why the heat of neutralisation of sulfuric acid is different to ethanoic acid

A

sulfuric acid: strong (dissociated/energy not needed to dissociate)

ethanoic acid: weak (undissociated/energy needed to dissociate)

117
Q

when calculating heats of combustion/formation

A
  • keep in mind moles in equation

- if no equation given, write the balanced equation so you know how many moles of each react!!

118
Q

importance of oil refining

A

give useful products / higher octane numbers

119
Q

balanced equation for combustion of ethanoic acid

A

CH3COOH + 2O2 –> 2CO2 + 2H2O

120
Q

combustion of a hydrocarbon formula

A

CₓHᵧ + ⁽⁴ˣ⁺ʸ⁾/⁴O₂ —> xCO₂ + ʸ/²H₂O

121
Q

using heat formula

A

If given in g, turn into kg, and turn kJ into J.
However, don’t convert the heat change if given in Kelvin to celsius, as the heat change would be the same in both units!!

122
Q

calculating heat of neutralisation

A

use mcθ to find heat produced in reaction, then divide by no. of moles (taking balanced equation into account) to find heat for 1 mole

LC Chemistry (26 decks)

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