3.3.2-Alkanes Flashcards
What is petroleum
It is a complex mixture of hydrocarbons
2 features of petroleum
Mainly alkanes which are hydrocarbons
When first extracted is almost useless
How is petroleum separated
Fractional distillation
3 key points of fractional distillation
Relies on hydrocarbon chains length being different so bp are different
Long chains have higher boiling point than short Chains
Long chains move toward bottom and short chains to top
Uses of fractions
Fuels
Petrochemicals
Feedstock for cracking
Why do we do cracking
There are a shortage of some chain length and a surplus of others as well alkenes are in high demand to make polymer which can only be found through cracking
What does a high mr make after cracking
Small mr + alkenes + hydrogen
What are the conditions of thermal cracking
High temperature 400-600
High pressure (7,000Kpa)
What are the products of thermal cracking
Alkenes
What are the uses of the products from thermal cracking
Chemical feedstock and conversion to polymers
Thermal cracking
Conditions
Products
Uses
High temperature
High pressure
Alkenes
Chemical feedstock and conversion to polymers
Catalytic cracking
Conditions
High temp -450
Slight pressure
Zeolite catalyst
Products of catalytic cracking
Branched alkanes, cyclohexane, aromatic hydrocarbons
Uses of products of catalytic cracking
Motor fuels
Methane use when burned
Natural gas, cooking , heating , electric
Combustion of propane uses
Camping fuel , domestic fuel and industrial fuel
Combustion of butane uses
Camping fuel and lighters
Uses of octane combustion
In petrol
What is complete combustion conditions and products
Excess of oxygen
Products CO2 and H20
What are conditions and products of incomplete combustion
Limited supply of oxygen
Products CO,C and H2O
CO is poisonous
What are the the pollutant produced by car engines
CO
NOx
Unburnt hydrocarbons
How is Co formed and the problem
Incomplete combustion
Poisonous gas
How are NOx formed and the problem
N2 and O2 react at high temperatures in engine
Combine with water to make acid rain and chemical smog
How NOx forms acid rain equation
4NO+O2+H2O - HNO3
How does NOx form chemical smog equation
4NO+O2+2H2O - 4HNO3
How are unburnt hydrocarbons formed and the problem
Engine not hot enough
Makes photochemical smog irritating to lungs
What is a catalytic converter
Catalytic converters are honeycomb of ceramic material coated with catalytic metals in thin layers
Examples of catalysts
Platinum, palladium , rhodium
How is NOx and CO changed to harmless gas in catalytic converter
NOx
C
Adsorb onto catalyst and react to form N2 and CO2
2NO+2CO- N2 +2CO2
NO2 +4CO - N2 + 4CO2
How do unburnt hydrocarbons change to unharmful compounds
React with NO to produce CO2 and H20 and N2
C8H18+25NO-8CO2+9H2O+12.5H2O
What happens when fossil fuels contain sulphur
S+O2 burns to make SO2
This goes into the air
What is the problem with SO2
SO2 in the air with water forms H2SO3 which is acid rain
How do you remove SO2
FGD(flue gas desulphisers)
Passed through CaO
SO2+ CaO–CaSO3
Oxidised
CaSO3+1/2O2 – CaSO4
How can CaSO4 be used after it is formed
Can be used as gypsum in plaster
What are the greenhouse gases
Carbon dioxide
Methane
Water
What do the greenhouse gases do
Absorb some of infa-red energy
Molecules then emit energy in all directions
Some returns to surface to keep warm
Impact of global warming
Ice in polar regions are melting and retreating
Sea levels rising
