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Chemistry > 4 Crude oil > Flashcards

4 Crude oil Flashcards

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1
Q

What is crude oil?

A

It is a mixture of hydrocarbons, compounds containing carbon and hydrogen only.

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2
Q

What did it form from?

A

Dead plants and animals that were living in the sea.

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3
Q

What are the physical properties of hydrocarbons that change with the increasing size of a molecule?

A
  • Boiling point increases.
  • The liquid becomes less volatile.
  • the liquids become more viscous and flow less easily.
  • The liquids become darker in colour.
  • Bigger hydrocarbons do not burn as easily as smaller hydrocarbons
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4
Q

Why does the boiling point increase?

A

The larger the molecule, the higher the boiling point. This is because large molecules have larger intermolecular forces of attraction between the molecules. Therefore, more energy is needed to break these stronger intermolecular forces of attraction to produce the widely separated molecules in the gas.

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5
Q

Why do the liquids become less volatile?

A

The bigger the hydrocarbon, the more slowly it evaporates at room temperature. This is because of the strong intermolecular forces of attraction to their neighbouring molecules and so they don’t turn into a gas more easily.

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6
Q

Why do the liquids become more viscous and flow less easily?

A

Liquids containing small hydrocarbon molecules are runny. Those containing large molecules flow less easily because of the stronger intermolecular forces of attraction.

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7
Q

What accompanies the fact that bigger hydrocarbons do not burn as easily as smaller ones.

A

This limits the use of bigger ones as fuels.

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8
Q

What has to happen to crude oil before it is used?

A

It has to be separated into fractions before it can be used.

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9
Q

What are the fractions?

A

These fractions are all mixtures, but each one contains a narrow range of sizes of hydrocarbons with similar boiling points.

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10
Q

Where is fractional distillation carried out? (For the separation of crude oil)

A

At an oil refinery.

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11
Q

How does fractional distillation work?

A
  • Crude oil is heated until it boils and its vapours pass into a fractionating column, which is hotter at the bottom and cooler at the top.
  • Smaller molecules have lower boiling points and get further up the column before they condense. Longer chain hydrocarbons have higher boiling points and condense lower down in the column.
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12
Q

What is the factor that controls how far up a particular hydrocarbon moves?

A

The boiling point.

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13
Q

What do all hydrocarbons burn in air (oxygen) to form?

A

Carbon dioxide and water and it releases a lot of heat.

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14
Q

What is fuel?

A

It’s a substance that when burned, releases heat energy.

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15
Q

What is incomplete combustion?

A

It occurs when there isn’t enough air, or oxygen.

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16
Q

What does incomplete combustion form?

A

Carbon (soot), or carbon monoxide.

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17
Q

Why is carbon monoxide dangerous?

A

It is colourless and odourless, and is very poisonous. It is poisonous because it reduces the ability of the blood to carry oxygen around the body. This could make you sick or maybe even die because not enough oxygen gets to the cells in your body for it to carry out respiration.

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18
Q

What is the formula of incomplete combustion when there is an excess of oxygen?

A

… + O2 —> CO + H2O
or
… + O2 —> C + H2O

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19
Q

What is complete combustion?

A

It is when carbon and hydrogen combine with oxygen to produce carbon dioxide and water.

20
Q

What does complete combustion form?

A

Carbon dioxide and water.

21
Q

What is the word equation for complete combustion?

A

Hydrocarbon + oxygen –> Carbon dioxide + water

22
Q

What is the symbol equation for complete combustion?

A

___ + O2 –> CO2 + H2O

23
Q

What are the main types of fractions and what are their uses?

A
  • Refinery gases.
  • Gasoline (petrol).
  • Kerosene.
  • Diesel.
  • Fuel oil.
  • Bitumen.
24
Q

What are refinery gases?

A

Refunery gases are a mixture of methane, ethane, propane and butane, which can be separated into individual gases if required.

25
Q

What is gasoline?

A

Petrol is a mixture of hydrocarbons with similar boiling points. It is used as a fuel in cars.

26
Q

What is kerosene?

A

It is used as a fuel for jet aircraft, as domestic heating oil and as ‘paraffin’ for small heaters and lamps.

27
Q

What is diesel?

A

This is used as a fuel for buses, lorries, some cars and some railway engines. Some is also converted to other more useful organic chemicals, including petrol, in a process called cracking.

28
Q

What is fuel oil?

A

This is used as a fuel for ships and for industrial heating.

29
Q

What is bitumen?

A

It is a thick, black material, which is melted and mixed with small pieces of rock to make the top surface of roads.

30
Q

What are some problems associated with the burning of fossil fuels from crude oil?

A
  • Climate change.
  • Acid rain.
31
Q

How does the burning of fossil fuels from crude oil contribute to climate change?

A

The carbon dioxide produced when hydrocarbons are burned is a greenhouse gas.
Greenhouse gases trap the heat radiated from the earths surface (the sun) and many people believe that this could lead to climate change.

32
Q

What is acid rain?

A

Acid rain is formed when water and oxygen in the atmosphere react with sulfur dioxide to produce sulfuric acid, or with various oxides of nitrogen, to give nitric acid.

33
Q

How does the burning of fossil fuels contribute to acid rain? (Sulfur)

A
  • Fossil fuels contain a small amount of sulfur.
  • This sulfur reacts with oxygen, producing sulfur dioxide.
  • Reactions in the atmosphere can convert this to sulfuric acid, which is a strong acid and component of acid rain.
34
Q

How does the burning of fossil fuels contribute to acid rain? (Nitrogen)

A
  • The temperature reached in the engine of a car is high enough to allow nitrogen and oxygen in the air to combine and produce oxides of nitrogen.
  • These nitrogen oxides can be converted into nitric acid in the atmosphere and therefore contribute to acid rain.
35
Q

What effect does acid rain pose to the environment.

A

Acid rain kills trees and fish in lakes.

36
Q

What is cracking?

A

It is a process in which long-chain alkanes are converted into alkenes and shorter chain alkanes

37
Q

Why is cracking used?

A

Some fractions are more useful and more profitable to sell than others.

38
Q

What is the problem in which that the amounts of each fraction obtained will depend on the proportions of the various hydrocarbons in the original crude oil, and not in the amounts in which they are needed?

A
  • There are far too many long-chain hydrocarbons, which are not in such high demand and are not as profitable to sell.
  • There are not enough shorter-chain hydrocarbons that can be used as fuel for cars.
39
Q

What is an example of what I just said above, in reference to petrol?

A

Far more petrol is needed that can be supplied by just separating crude oil into its fractions.

40
Q

How does catalytic cracking work?

A
  • The fuel oil fraction is heated to give a gas and then passed over a catalyst of silicon dioxide and aluminium oxide at about 600 - 700 *C.
41
Q

What is cracking an example of?

A

Thermal decomposition, this is when a big molecule split into smaller ones on heating.

42
Q

What happens to the bonds of the hydrocarbons during cracking?

A

C-C single bonds are broken and new C=C double bonds are formed.

43
Q

What kind of products does cracking form?

A

A mixture of alkanes and alkenes.

44
Q

What are some important reasons as to why oil companies carry out cracking?

A
  • To produce more petrol.
  • to produce more alkenes that can be used for making polymers (plastics). Alkenes are more reactive than alkanes and also have other uses.
45
Q

Why is catalytic cracking so important?

A

The products produced are usually highly useful and sought-after in the chemical industry

Chemistry (22 decks)

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