Crude oil, Fuels and Organic chemistry Flashcards
What is crude oil made of?
A complex mixture of hydrocarbons
What are hydrocarbons made of?
Compounds that contain hydrogen and carbon atoms only
How was crude oil formed?
Fossilisation under pressure and heat at the bottom of the sea from dead marine organisms over millions of years
What is fractional distillation?
A way of separating out different ‘fractions’ of the oil.
Why does fractional distillation work?
The different compounds in crude oil have different boiling points.
How does fractional distillation work?
The oil is heated causing it to boil and turn into a gaseous mixture and as the vapour rises in the fractionating column it cools.
As it cools the chemicals with higher boiling points will be the first to start to condense.
At various points the condensing liquid is extracted.
In fractional distillation the larger the molecule …
The larger the molecule to higher its boiling point will be so the extracted molecules get smaller as you go up.
What do you get out of the fractions?
The fractions are not pure chemicals, but a mixture of alkanes with similar boiling points.
What must you do to hydrocarbons before melting/boiling them and why?
The molecules of hydrocarbons are held together by intermolecular forces which have to be broken for the hydrocarbon to melt or boil. The longer the hydrocarbon, the more intermolecular forces so more energy is needed to break them.
The increased number of intermolecular forces …
The increased number of intermolecular forces also makes the longer chain hydrocarbons more viscous (less easy to pour, thicker liquids)
As chain length increases …
Boiling point and melting point increases
Viscosity increases
Colour darkens
Flammability decreases
What must happen for a fuel to burn?
For a fuel to burn it must vapourized as it is the vapour that burns.
What makes a fuel easier to transport?
It is also useful for a fuel to have a low viscosity so that it can be piped from place to place.
What is collected at the top of the fractional distillation column?
Shorter hydrocarbons are collected nearer the top (lower boiling points)
What is collected at the bottom of the fractional distillation column?
Longer hydrocarbons are collected near the bottom (higher boiling points)
Economic issues with the oil industry?
The price of oil is set by the oil producing countries so poorer countries heavily rely on them.
Wars and internal crisis’ within a country that produces oil can affect the flow of oil to other countries.
Political issues with the oil industry?
If a country depends on another country for supply they can hold them by ransom by cutting off their oil supply.
Social issues with the oil industry?
The oil industry supplies jobs and money for the economy.
Environmental issues with the oil industry?
Burning fossil fuels releases lots of CO₂ and greenhouse gasses into the atmosphere contributing to global warming and climate change.
Buildings are not attractive so ‘spoiling’ areas of countryside.
Oil spillages can result to considerable damage to local wildlife.
What is a combustion reaction?
A combustion reaction is a chemical reaction where a substance reacts with oxygen producing heat, light and new products.
When hydrocarbons burn they from?
Carbon dioxide and water
What can happen if there’s a limited supply of oxygen during combustion and what does it form?
If the supply of oxygen is limited then incomplete combustion can occur. This results in the formation of carbon and carbon monoxide as well as carbon dioxide and water.
Why is carbon monoxide bad?
Carbon monoxide is poisonous and odourless so it is important to avoid incomplete combustion
What do many fuels contain?
Many fuels contain a variety of impurities, most commonly compounds of sulfur.
What does burning fuels result in?
The formation of sulfur dioxide which can give rise to acid rain.
What can acid rain lead to?
Acid rain can lead to the death of trees and aquatic animals and the erosion of limestone buildings and statues.
How do you work out the energy released by fuels?
Energy transferred = Mass of water heated x Temperature rise x 4.2
What is hydrogen as a fuel?
Hydrogen is a combustible gas that can be used as a fuel as it produces no greenhouse gases when burned.
What is the chemical formula for hydrogen burning?
2H₂ + O₂ -> 2H₂O
What is the word formula for hydrogen burning?
Hydrogen + Oxygen -> Water
How is hydrogen made?
Hydrogen is mainly made by reacting steam with either coal or natural gas and electrolysis.
Is hydrogen a carbon neutral fuel?
No as the use of coal, gas and electricity means that manufacturing hydrogen produces CO₂.
Disadvantage of hydrogen as a fuel? (Burning)
Hydrogen is very flammable and can explode so potentially more dangerous.
Disadvantage of hydrogen as a fuel? (Storage)
For storage hydrogen must be cooled and compressed then kept in strong tanks, insulated. Liquid hydrogen needs to be kept at -250°C. Petrol and diesel are much easier to store and transport.
What does the fire triangle contain?
Oxygen
Fuel
Heat
Removal of oxygen?
CO₂ fire extinguishers and fire blankets deprive fire of oxygen.
Fire blankets seal off the fire and once the fire uses up the oxygen it goes out.
CO₂ extinguishers push the oxygen away.
Removal of heat?
Putting water on fires removes the heat however, this can’t be used on electrical/oil fires.
Removal of fuel?
Fuel resistant materials can ensure any fires that start will quickly stop.
Forest fire occurs what do you do to remove the fuel?
Cut down nearby trees.
What is cracking?
Breaking of longer chain hydrocarbons into shorter chains.
What does cracking involve?
Heating the hydrocarbons to vapourise them.
What happens to the vapours in cracking?
Passed over a hot catalyst of silica or alumina
Mixed with steam and heated to a very high temperature so that thermal decomposition reactions occur.