C1.4- Crude oils and fuels

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What is crude oil?
A mixture of lots of different chemical compounds
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What is a mixture?
Two or more chemical elements or compounds that are not chemically combined together.
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What must happen before the constituents of crude oil can be used?
They must be separated into substances with similar boiling points.
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What is a fraction?
A substance separated from crude oil that has a similar boiling point
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How are the fractions of crude oil separated?
Distillation
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What does this process rely on to separate the different fractions?
Different boiling points
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What is a hydrocarbon?
A compound found in crude oil containing almost only hydrogen and carbon
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What is the name given to most of the hydrocarbons in crude oil?
Alkanes
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What general formula can be used to work out the number of hydrogen and carbon atoms in alkanes?
CnH(2n+2)
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If a hydrocarbon has 15 carbon atoms how many hydrogen atoms will it have?
32
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Why are alkanes known as saturated?
They contain as many hydrogen atoms as possible in each molecule.
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Do long or short chain hydrocarbon molecules tend to be more useful?
Short chain
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What are these hydrocarbons useful for? Why?
Fuels as they burn well
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What is the boiling point of a hydrocarbon dependent on?
The size of the individual molecules (the chain length)
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What is fractional distillation?
The separation of hydrocarbons into fractions with similar boiling points
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As well as boiling point what else do the molecules in each fraction have in common?
They have a similar number of carbon atoms.
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Where is crude oil fed into the distillation tower? What state is it in?
Near the bottom as a hot vapour
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Where is the fractionating column hottest?
Near the bottom
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What happens as the crude oil vapour travels up the column?
The gases condense as they approach the point at which they turn back to liquid and are collected.
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Where are the hydrocarbons with the shortest chains collected?
At the top of the column
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Why are the lighter fractions from crude oil useful as fuels?
They produce energy when burnt with air and are highly combustible (burn easily).
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What is the definition of oxidised?
Forming oxides in a chemical reaction by adding oxygen
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What laboratory tests could you use to confirm the products of the combustion of hydrocarbons? What results would be seen?-
Blue cobalt chloride paper will turn pink in the presence of water.  Limewater will turn cloudy when carbon dioxide is bubbled through it. You would expect both to be positive.
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What impurities can fossil fuels contain?
Sulfur-containing substances
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What do these impurities produce when they react with oxygen?
Sulfur dioxide
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Why is this a problem?
Sulfur dioxide is poisonous and acidic (can cause acid rain and engine corrosion).
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Under what condition does incomplete combustion take place?
When there is not enough oxygen
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What is produced in incomplete combustion?
Carbon monoxide
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Why is this gas poisonous?
It replaces the oxygen carried by your red blood cells in your blood.
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What other waste product can be formed in car engines?
Nitrogen oxides
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Are the elements in this waste product from the fossil fuels themselves? If not, where are they from?
No, there is no nitrogen in fossil fuels. The nitrogen comes from the air when the engine is extremely hot.
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What are particulates?
Tiny solid particles produced when the longer hydrocarbon chains in diesel are not completely reacted with oxygen
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What is a big potential problem with particulates?
Scientists believe they could be linked to lung cancer.
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Why has pollution begun to be a bigger problem in the last 100 years?
There has been a huge increase in the use of fossil fuels.
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What is the main greenhouse gas?
Carbon dioxide
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What do most scientists think the increase in carbon dioxide is linked to?
Global warming / greenhouse effect
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What is global dimming?
When particulates travel into the atmosphere and reflect sunlight back into space
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Who is at particular risk from the effects of carbon monoxide?
People with heart problems
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What has been linked to the increase in amounts of sulfur dioxide and nitrogen oxides in the air?
An increase in asthma and acid rain
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What effects can acid rain have?
It can damage animals and plants (as well as limestone buildings).
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What effect does a catalytic converter have on car fumes?
It reduces the amount of carbon monoxide and nitrogen oxides produced.
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How are the precious metal catalysts arranged in catalytic converters?
So they have a very large surface area
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What reaction happens in a catalytic converter? Why is this beneficial?
Carbon monoxide + nitrogen oxides = carbon dioxide + nitrogen It is beneficial because it forms two much less harmful gases.
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What do catalytic converters not help?
The levels of carbon dioxide in the air are not reduced
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What can be used to remove particulates from diesel engines?
Filters
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What is flue gas desulfurisation?
When sulfur dioxide is removed from the waste products of power stations using calcium oxide or calcium hydroxide
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What other way can sulfur products be reduced?
By removing the sulfur from the fuel before it is burnt
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What are biofuels?
Fuels that are made from plant or animal products
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What is biodiesel made from?
Oils extracted from plants
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What is biogas made from?
Animal waste
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Why is biodiesel an advantage if there is a spill?
It breaks down much faster than normal diesel.
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How much sulfur dioxide is produced from biodiesel compared to diesel?
Much less sulfur dioxide
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Why is biodiesel likely to become more economically attractive in the future?
As resources of petrol and diesel run out their price will increase making biodiesel cheaper than them.
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Why is biodiesel referred to as ‘CO2 neutral’?
The crops that are grown to make biodiesel absorb CO2 which counters any that is produced when it is burnt.
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Why is the term ‘CO2 neutral’ a little misleading?
We need to also take into account the carbon dioxide produced during the production of biodiesel (fertilising, extracting and transport).
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What other useful products are made when producing biodiesel?
High energy cattle feed Glycerine for soap
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Why might biodiesel have a negative impact on poorer countries?
Farmland may be used to produce fuel instead of food; this could potentially put the price of staple foods up adding to the problems of famine in these countries.
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Why may biodiesel not be a suitable fuel in places like Siberia or Greenland?
It freezes at a lower temperature than normal diesel so may freeze in the tanks of cars in very cold climates.
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How is the ethanol biofuel produced?
By fermenting the sugar from sugar cane or sugar beet
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Why is using ethanol mixed with petrol better than using petrol alone?
The sugar cane and beet crops absorb CO2.
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Why would hydrogen be such a good fuel in terms of pollution?
It only produces water as a waste product.
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What are two potential problems with using hydrogen as a fuel?
It is explosive when ignited with air. It is a gas so takes up a lot more volume than regular liquid fuels.
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Other cards in this set

Card 2

Front

What is a mixture?

Back

Two or more chemical elements or compounds that are not chemically combined together.

Card 3

Front

What must happen before the constituents of crude oil can be used?

Back

Preview of the front of card 3

Card 4

Front

What is a fraction?

Back

Preview of the front of card 4

Card 5

Front

How are the fractions of crude oil separated?

Back

Preview of the front of card 5
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Comments

Lynx

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Good revision source :)

TheMentallBental

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yery good

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