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Chemistry > Oil refining, fules and thermochemistrey > Flashcards

Oil refining, fules and thermochemistrey Flashcards

1
Q

what are fossil fules

A

fossil fules are formed from the remains of plants and animals that lived millions of years ago

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2
Q

what is natural gas

A

a mixture of hydrocarbons-primarliy methane

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3
Q

how is methane produced?

A
  1. animal waste and dead plants allowed to be decomposed by anaerobic bacteria producing methane
    2.naturally prouced in slurry pits,coal mines and refuse dumps
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4
Q

Give an advantage of methane production

A

methane is a very good fuel

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5
Q

outline a hazard of methane production

A

accidents have occoured in mines as methane forms an explosice mixture with air and exposives have occoured

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6
Q

give a disatvantage of methane production

A

its one of the leading gasses that causes greenhouse effect leading to global warming

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7
Q

what is crude oil/petroleum

A

crude oil is a type of oil that is a mixture of many different hygrocarbons

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8
Q

wha is fractional distillation/fractionation of crude oil

A

a distillation that is used to separate crude oil into its component hydrocarbons based on their specific molecular mass/boiling point

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9
Q

How is fractional distillation carries out?

A

The crude oil at base column is heated and mostly becomes a vapour
moved up through the column, the temperture decreases going up. The different factions of hydrocarbons condense into a liquid once they cool below their specific cooling point and are collected on a specific tray
the larger molecules wiht higher boiling points are collected at lower levels. The smaller molecules with lower boiling points are collected at higher levels

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10
Q

Based on what two properties of the hydrocarbons are they separated into their different fractions?

A

Their boiling points
Their molecular mass

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11
Q

Name the fractions and their uses and their chain length from lightest to heaviest

A

Refinery Gas C1-C4
-Domestic gas (LPG)

Light gasoline C5-C10
-Petrol for cars

Naphtha C7-C10
-Petrol for cars
-Feedstock for the petrochemical industry to make plastics, solvents,detergents

Kerosene Paraffin Oil
C10-C14
-Fuel for jet aircraft
-Oil for home central heating

Gas Oil (Diesel oil)
C14-C49
-Diesel for vehicles
Lubricant for engines

Residue
C35 and higher
Bitumen for road surfacing, roofing and waterproofing

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12
Q

why is the bottom fraction known as the residue fraction?

A

this is the fraction left over as a liquid at the bottom of the fractionating column and the other more volatile fractions turn to gasses and travel upwards

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13
Q

what does LPG stand for

A

liquid petroleum gas

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14
Q

what are the main components of LPG
what is LPG used for

A

propane and butane mixture
it is sold as domestic gas for heating and cooking

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15
Q

what are mercaptans and why are they used

A

mercaptans are sulfur containing compounds
they are added to natural gas(methane) and liquid petroleum gas to give them a unpleasent smwll to warn of gas leaks

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16
Q

what fractions in fractional distillation can be used as petrol

A
  1. light gasoline
  2. Naphtha
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17
Q

what is petrol composed of?

A

a mixture of different hydrocarbons,mostly chain lenght C5-C10 alkanes

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18
Q

How is petrol used as motor fuel?

A

In the engine of a car, a mixture of petrol and oxygen is ignited by spark plugs
the ‘explosion’ provides power to turn the wheels

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19
Q

what is auto-ignition/ knocking of the engine? why is it bad for the engine

A

The premature ignition of he petrol-air mixture before a spark is produced by spark plugs.
it results in loss of power and damage the engine

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20
Q

what property of petrol leads to auto-ignition?

A

petrol containing long unbranched straight chained alkanes eg heptane

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21
Q

what is ment by octane number

A

measure of a tendency of a fuel to resist auto ignition

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22
Q

factors affecting a fuels octane number

A

lenght of chain- shorter chain= better octane number
degree of branching- the more branched= the higher octane number
cyclic structure- cyclic compounds hacr a higher octne number than straight chain

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23
Q

how is a fuel given an octane number, name the compounds that have the octane number of 0 and 100

A

two refrence compounds are used
Heptane has a octane number of 0
2,2,4-teimethylpentane has a octane number of 100the performance of the fuel is compared with know mixtures of heptane and 2,2,4 trimethylpentane and given a suitable octane number

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24
Q

why is lead no longer added to petrol to increase octane number?

A

lead is harmful to the enviorment and peoples health
lead poisond the catalytic converter in cars

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25
name the three processes to improve the octane number/ avoid adding lead/ reduce its tendency to auto-idnite
isomerisation dehydrocyclisation catalytic cracking
26
what is isomerisation? breifly describe the process
Isomerisation involves the changing straight chain alkanes into branched compounds with the same molecular formula but different structural formula. straight chain alkanes are heated causinf chains to break
27
What is dechydrocyclisation?
dehydrocyclisation is the use of a catalyst to cause a straight chained hydrocarbon lose its hydrogen forming a ringed compound
28
give a second advantage of peforming dehydrocyclisation aside from increasing octane number. Name the used of that product
hygrogen is also produced hydrogen can be used for -ammonia production -make margarine -a fuel
29
what is catalytic cracking
catalytic creacking involves using heat and a catalyst to break down lond chained hydrocarbons for which there is low demand into shorter chained molecules for which there is a greater demand ( you always get an alkene at least)
30
give an second advantage of performing catalytic cracking aside from increasing octane number
alkenes are also formed, alkenes are widly used in the petrochemical industry to make plastics
31
describe the addtion of oxygenates
addition of compounds that contain oxygen to the petrol
32
give two examples oxygenates that can be added to petrol
a. methanol, ethanol b.MTBE (metyl tert-butyl ether) these compounds increase the octane number of the poetrol
33
give a second atantage of addition oxygenates to petrol aside from increaing octane number
petrol containing oxygenates also give rise to much less pollution
34
name three ways hydrogen is manufactured on a large scale
-steam reformation of natural gas -electrolysis of water -dehydrocyclosation of hydrogen
35
what is the balanced chemical equation of steam reformation of natural gas
CH4 + H2O -> 3H2 + CO
36
what is eletrolysis of water, give a balanced equation
hydrogen gas collecrs at the negative electrofe/cathode 2H2O-> 2H2 + O2
37
how does dehydrocyclisation of a hydrocarbon produce hydrogen?
produces hydrogen gas as a bi-product
38
give three uses of hydogen gasses
manufature of ammonia, known as tge haber process, ammonia is used in fertilisers,cleaners and bleaches hydrogenation of vegtable oil to make margarine potetial to use as a fuel
39
give two advantages of using hydrogen as a fuel
hydrogen is a clean fuel- water is the only product of its combustion hydrogen burns efficiently as a fuel- it has a high kilogram calorific value: a lot of energy is given our per kg burned in oxygen
40
give a disadvantage of using hydrogen as a fuel
hydrogen is explosive with oxygen- problems with storage and transportation
41
what is used to describe heat change
ΔH
42
what is an exothermic reaction
a reaction that produces and gives out heat to its surroudings it has a negative ΔH value and produces an increase in temperture
43
what in an endothermic reaction
a reaction that takes in heat from its surounddings has a postive ΔH valur and decreases in temperture
44
what is heat of formation?
heat of formation is the heat change that ocoours when one mole of a substance is formed from elements in standard states (right hand side cannot be changed)
45
what is heat of combustion
the heat change that occours when one mole of a substance os completely burned in excess oxygen (1 mole on left hand side)
46
what do all organic compunds form when burned in oxygen?
CO2 and H2O
47
What piece of apparatus in the laboratory can be used to measure the heats of combustion of substances such as fuel or foodstuffs
a bomb calorimeter
48
describe how a bomb calorimeter works
a known mass of the substance is places in the crucibe in the bomb. bomb is placed in a known volume of water. the substance is ignited electrically and allowed to burn in excess oxygen the change in temperture in water is recorded heat produced is calculated using formula m x c x ΔH the heat produced for one mole is calculated
49
what is kilogram calorific value
kilogram calorific value is the heat energy produced when 1 Kg of a fuel is burned completely in excess oxygen
50
the heat combustion of methane is -890 kj MOL-1. calculate thee kilogram calorific value of methane
convert 890 Kj mol-1 calculate the kilogram calorific value of methane divide 16/1000 to get per kg. 890 divide by 0.016 and multiply by 1 to get -55625
51
give two reasons my methane is an excellent fuel
methane has a very high kilogram calorific value- a lot if energy is given out per kg burned in oxygen methane is a pure subtance and burns with a clean flame
52
define bond energy
bond energy is the average energy required to break one mole of a particular colvalent bond and to sseparate the netrual atoms completely from eachother
53
what is heat of reaction
heat of reaction is the heat change that occours when the number of moles given in a balanced equation react completely
54
What is hess's law
hess's law sates that if a chemical reaction takes place in a number of stages, the sum of the heat changes in seperate stages is equal to the heat change if the reaction is carried out in one stage A+b+C+D = a -> D
55
What is heat of neutralisation
The heat change that occurs when 1mole of H+ ions from and acid reacts with 1 mole of OH- ions from a base it is always exothermic (always negative ΔT value)
56
Describe the procedure of defining the heat of reaction of hydrochloride acid with sodium hydroxide ie.heat of neutralisation
Using a graduated cylinder add hydrochloric acid to a polystyrene cup and add sodium hydroxide to a separate polystyrene cup. Record the temp 1( if the two are not equal, calculate their average) Record the max temperature obtained T2. Record the rise in temperature and calculate the heat for the reaction using m X c X ΔT and hence the heat of reaction/netralisation
57
Name another way to increase octane number
addition of oxygenates
58
Why are polystyrene cups used in this expeirment ## Footnote Dertimining the heat of reaction of hydrochloride acid with sodium hydroxide ie.heat of neutralisation
- They are excellent insulators and will only allow a minimal heat loss to surroundings - they have a negligible heat compacity- they will absorb a neglugible amount of heat away from the reaction
59
Give an advantage and disadvantage of using a pipette/burette to measure out the solitions. ## Footnote Dertimining the heat of reaction of hydrochloride acid with sodium hydroxide ie.heat of neutralisation
**Advantage** a pipette is more accurate than a graduated cylinder **Disadvantage** a pipette is very slow to measure out solutions
60
If the hydrochloric acid and sodium hydroxide solutions had been stored at slightly different temperatures, explain how the initial temperature of the reaction mixture could have been obtained ## Footnote Dertimining the heat of reaction of hydrochloride acid with sodium hydroxide ie.heat of neutralisation
An average temperture of the two solutions is essential
61
How do we know the reaction if the HCl and NaOH is exothermic ## Footnote Dertimining the heat of reaction of hydrochloride acid with sodium hydroxide ie.heat of neutralisation
the temperture rises; exothermic reactions have a rise in temperture
62
Give two reasons why the stirring od the solutions is essential ## Footnote Dertimining the heat of reaction of hydrochloride acid with sodium hydroxide ie.heat of neutralisation
to distribute the heat evenly and take accurate temperture readings to ensure the the solutions react completely
63
give three percautions that should be taken to accurately measure the change in temperture ## Footnote Dertimining the heat of reaction of hydrochloride acid with sodium hydroxide ie.heat of neutralisation
-Once the solutioms are mixed quickly cover the polystyrene cup with a lid to avoid heat loss to surroundings -ensure no splashing and loss of volume of liquid occours-leads to innacurate results -a sensitive thermometer is used ( one that reads to at least 0.1C )
64
after the temperature of the mixed acid and base solution rises, the temperture will then gradually drop. What is the reason for this? ## Footnote Dertimining the heat of reaction of hydrochloride acid with sodium hydroxide ie.heat of neutralisation
the temperture of the solutions after mixing will be greater than room temperture, heat will be lost to the surroundings
65
why are concentrated solutions of hydrocloric acid and sodium hydroxide used? ## Footnote Dertimining the heat of reaction of hydrochloride acid with sodium hydroxide ie.heat of neutralisation
- concentrated solutions are used to obtain a significant rise in temperture - a larger temperture rise is easier to measure accuratelu and will have less percentage error
66
Give two saftey percautions ## Footnote Dertimining the heat of reaction of hydrochloride acid with sodium hydroxide ie.heat of neutralisation
as concentrated solutions of HCl and NaOH are being used, they are corrosive and cause burns saftey glasses are worn gloves and lab coat are worn
67
state and explain two futher modifications that could be made if the value for heat neturalisation was lower than expected ## Footnote Dertimining the heat of reaction of hydrochloride acid with sodium hydroxide ie.heat of neutralisation
-more insulation- a more accurate rise in temperture would be recorded
68
why will the same temperture rise be recorded if 3 times the volume of HCl and NaOH was used ## Footnote Dertimining the heat of reaction of hydrochloride acid with sodium hydroxide ie.heat of neutralisation
three times the volume produces three times the heat but this heat spreads itself throughout three times a greater volume. therefore the tempertur rise is the same
69
define specific heat capacity
the amount of heat required to raise the temperture of 1 kg of a substance by 1 kelvin
70
what is the formula for the heat produced in the reaction
- (m X c X ΔT) C (m x c)= (total heat capacity)
71
what is heat of reaction/ netralisation formula?
heat produced (step 2)/ number of moles of acid (step 1)

Chemistry (36 decks)

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