Oil refining, fules and thermochemistrey Flashcards
what are fossil fules
fossil fules are formed from the remains of plants and animals that lived millions of years ago
what is natural gas
a mixture of hydrocarbons-primarliy methane
how is methane produced?
- 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
Give an advantage of methane production
methane is a very good fuel
outline a hazard of methane production
accidents have occoured in mines as methane forms an explosice mixture with air and exposives have occoured
give a disatvantage of methane production
its one of the leading gasses that causes greenhouse effect leading to global warming
what is crude oil/petroleum
crude oil is a type of oil that is a mixture of many different hygrocarbons
wha is fractional distillation/fractionation of crude oil
a distillation that is used to separate crude oil into its component hydrocarbons based on their specific molecular mass/boiling point
How is fractional distillation carries out?
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
Based on what two properties of the hydrocarbons are they separated into their different fractions?
Their boiling points
Their molecular mass
Name the fractions and their uses and their chain length from lightest to heaviest
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
why is the bottom fraction known as the residue fraction?
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
what does LPG stand for
liquid petroleum gas
what are the main components of LPG
what is LPG used for
propane and butane mixture
it is sold as domestic gas for heating and cooking
what are mercaptans and why are they used
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
what fractions in fractional distillation can be used as petrol
- light gasoline
- Naphtha
what is petrol composed of?
a mixture of different hydrocarbons,mostly chain lenght C5-C10 alkanes
How is petrol used as motor fuel?
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
what is auto-ignition/ knocking of the engine? why is it bad for the engine
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
what property of petrol leads to auto-ignition?
petrol containing long unbranched straight chained alkanes eg heptane
what is ment by octane number
measure of a tendency of a fuel to resist auto ignition
factors affecting a fuels octane number
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
how is a fuel given an octane number, name the compounds that have the octane number of 0 and 100
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
why is lead no longer added to petrol to increase octane number?
lead is harmful to the enviorment and peoples health
lead poisond the catalytic converter in cars
name the three processes to improve the octane number/ avoid adding lead/ reduce its tendency to auto-idnite
isomerisation
dehydrocyclisation
catalytic cracking
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
What is dechydrocyclisation?
dehydrocyclisation is the use of a catalyst to cause a straight chained hydrocarbon lose its hydrogen forming a ringed compound
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
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)
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
describe the addtion of oxygenates
addition of compounds that contain oxygen to the petrol
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
give a second atantage of addition oxygenates to petrol aside from increaing octane number
petrol containing oxygenates also give rise to much less pollution
name three ways hydrogen is manufactured on a large scale
-steam reformation of natural gas
-electrolysis of water
-dehydrocyclosation of hydrogen
what is the balanced chemical equation of steam reformation of natural gas
CH4 + H2O -> 3H2 + CO
what is eletrolysis of water, give a balanced equation
hydrogen gas collecrs at the negative electrofe/cathode
2H2O-> 2H2 + O2
how does dehydrocyclisation of a hydrocarbon produce hydrogen?
produces hydrogen gas as a bi-product
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
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
give a disadvantage of using hydrogen as a fuel
hydrogen is explosive with oxygen- problems with storage and transportation
what is used to describe heat change
ΔH
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
what in an endothermic reaction
a reaction that takes in heat from its surounddings
has a postive ΔH valur and decreases in temperture
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)
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)
what do all organic compunds form when burned in oxygen?
CO2 and H2O
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
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
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
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
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
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
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
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
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)
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
Name another way to increase octane number
addition of oxygenates
Why are polystyrene cups used in this expeirment
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
Give an advantage and disadvantage of using a pipette/burette to measure out the solitions.
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
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
Dertimining the heat of reaction of hydrochloride acid with sodium hydroxide ie.heat of neutralisation
An average temperture of the two solutions is essential
How do we know the reaction if the HCl and NaOH is exothermic
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
Give two reasons why the stirring od the solutions is essential
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
give three percautions that should be taken to accurately measure the change in temperture
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 )
after the temperature of the mixed acid and base solution rises, the temperture will then gradually drop. What is the reason for this?
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
why are concentrated solutions of hydrocloric acid and sodium hydroxide used?
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
Give two saftey percautions
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
state and explain two futher modifications that could be made if the value for heat neturalisation was lower than expected
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
why will the same temperture rise be recorded if 3 times the volume of HCl and NaOH was used
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
define specific heat capacity
the amount of heat required to raise the temperture of 1 kg of a substance by 1 kelvin
what is the formula for the heat produced in the reaction
- (m X c X ΔT)
C (m x c)= (total heat capacity)
what is heat of reaction/ netralisation formula?
heat produced (step 2)/ number of moles of acid (step 1)
