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What happens during fractional distillation?
Crude oil is heated to vaporise it
The vapour is passed into the column
The top of the tower is cooler than the bottom (negative temperature gradient)
Fractions are separated out by their bpt
Low bpt fractions collected at the top
What is cracking?
I process where long chain hydrocarbons are broken into smaller chain hydrocarbons
Requirements and results of thermal cracking?
High temp (1200K)
High pressure (7000Kpa)
Large proportion of alkenes and lower proportion of branched alkanes
Requirements and results of catalytic cracking?
Relatively low temp (700K)
Slightly above atmospheric pressure
Large proportion of branched alkanes and arenes
Uses a zeolite catalyst
Why is zeolite a good catalyst?
It’s structure gives it a high surface area
What is the solid pollutant in incomplete combustion?
Carbon (soot)
What is the gaseous pollutant in incomplete combustion?
Carbon monoxide
How is nitrogen monoxide formed and what is the equation showing this?
Temperatures in internal combustion engines can reach very high temperatures over 2000oC
Strong N2 triple covalent bonds are broken
This allows nitrogen and oxygen to react
N2 + O2 → 2NO
How is nitrogen dioxide formed from combustion engines?
NO can further react with oxygen to produce NO2
NO + 1/2O2 → NO2
How is nitric acid formed and what affect does this have on the environment?
Nitrogen dioxide can react with rain water and more oxygen to produce nitric acid which contributes to acid rain
2NO2 + H2O + 1/2O2 → 2HNO3
What are the effects of acid rain?
Corrodes buildings
Lowers pH of rivers and streams, affecting photosynthesis, killing plants eventually leading to the death of fish
Lowers the pH of soil which can affect microorganisms and crops
What is the release of unburnt hydrocarbons linked to?
Cancer
What are catalytic converters and what are they made of?
Used to transform pollutants gasses in a car’s exhaust into less harmful gasses
Contains a honeycomb structure for a high surface area
Equation for the removal of CO in a catalytic converter
CO + ½ O2 → CO2
Equation for the removal of CO and NO in a catalytic converter
CO + NO → CO2 + ½ N2
Equation for the removal of NO in a catalytic converter
2NO → N2 + O2
Equation for the removal of unburnt hydrocarbons in a catalytic converter
Hydrocarbon + Oxygen → Carbon dioxide + water
Basically a combustion equation
Equation for the removal of unburnt hydrocarbons and NO in a catalytic converter
Hydrocarbon + NO→ CO2 + N2 + H2O
How do catalytic converters work?
NO is adsorbed by the catalyst
Attaches to surface forming weak IMF
This weakens the bond within the molecule so it is broken
Nitrogen and Oxygen desorbed from the catalyst and IMFs disappear
Why is sulfur impurities in fossil fuels a problem and where does it come from?
It burns in oxygen to produce SO2
It can be further oxidised into SO3
Both of these can react with water to form sulfurous and sulfuric acid
Equations for the formation of sulfur dioxide and sulfur trioxide
S + O2 → SO2
SO2 + ½ O2 → SO3
Equations for the formation of sulfurous acid and sulfuric acid
SO2 + H2O → H2SO3
SO3 + H2O → H2SO4
How can sulfur dioxide be remove from flue gasses?
Flue gas desulphurisation
S reacts with calcium oxide or calcium carbonate and is neutralised
What are the equations that show what happens in lue gas desulphurisation?
CaO + SO2 → CaSO3
CaCO3 + SO2 → CaSO3 + CO2