Organic chemistry

Question 1

What is crude oil?

Answer 1

Crude oil is a fossil fuel found in rocks. Fossil fuels are natural substances. Crude oil is a mixture of a very large number of different compounds. Most of these compounds are hydrocarbons.

Question 2

How is crude oil formed?

Answer 2

It’s found in the Earth’s crust. Millions of years ago small animals and plants died and fell to the bottom of the sea. Their remains were covered by mud. The mud eventually turned to rock. This rock put a lot of pressure on the dead animals and plants. Rocks around them also heated them up. Together the heat and the pressure turned the remains into crude oil. It was important that no air or oxygen was present. Other rocks above the oil were impermeable (not porous). The oil could not float upwards through these rocks and so it gets trapped underneath it. Geologists - rock scientists - can often tell where oil may be trapped.
Oil companies can drill down through the impermeable rocks to get it out. They are then able to turn it into products we can use.

Question 3

What is a hydrocarbon?

Answer 3

Hydrocarbons are compounds formed from carbon and hydrogen only.

Question 4

What are the first ten alkanes in order?

Answer 4

1) methane
2) ethane
3) propane
4) butane
5) pentane
6) hexane
7) heptane
8) octane
9) nonane
10) decane

Question 5

What is an Alkane?

Answer 5

Are the simplest type of hydrocarbon. An alkane is a hydrocarbon with single covalent bonds. Alkanes are saturated (single bonds)

Question 6

What is an alkene?

Answer 6

They are unsaturated (double bonds)

Question 7

What is complete combustion?

Answer 7

The complete combustion of a hydrocarbon in oxygen releases lots of energy. This makes them useful as fuels. The only waste products are carbon dioxide + water vapour
During combustion, both carbon dioxide and hydrogen from the hydrocarbon are oxidised. Oxidation is the gain of oxygen.

Question 8

What is incomplete combustion?

Answer 8

Shortage of oxygen when hydrocarbon fuel is burned. Incomplete combustion can produce carbon monoxide and water.

Question 9

What is the equation for complete combustion?

Answer 9

Hydrocarbon+oxygen goes to carbon dioxide+water

Question 10

What is the use of petroleum gases (such as propane and butane)?

Answer 10

Used as fuel in heating appliances, cooking equipment, and vehicles.

Question 11

What is the use of kerosene?

Answer 11

Used for aircraft fuel ⛽️

Question 12

What is the use of lubricating oil?

Answer 12

It is a class of oils used to reduce the friction, heat, and wear between mechanical components that are in contact with each other. Lubricating oil is used in motorized vehicles

Question 13

What is the use of heavy fuel oil?

Answer 13

Heavy fuel oil or residual oil is a by-product of crude oil refining process, containing a lot of the contaminants removed from the lighter oils. This makes it much cheaper than other lighter marine fuels and is the main reason it is used in marine engines.

Question 14

What is the use of bitumen?

Answer 14

In road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.

Question 15

How high does crude oil have to be heated up to?

Answer 15

About 360degrees

Question 16

Is it hot or cool at the bottom of a fractionating column?

Answer 16

Hot

Question 17

Is it hot or cool at the top of the fractionating column?

Answer 17

Cool

Question 18

What is the method for fractional distillation?

Answer 18

1) crude oil is heated until most of it has turned into gas. The gases enter a fractionating column (and the liquid bit is drained off).
2) in the column there’s a temperature gradient (it’s hot at the bottom and gets cooler as you go up)
3) the longer hydrocarbons have high boiling points. They condense back into liquids and drain out of the column early on, when they’re near the bottom. The shorter hydrocarbons have lower boiling points. They condense and drain out much later on, near the top of the column where it’s cooler.
4) you end up with the crude oil mixture separated out into different fractions. Each fraction contains a mixture of hydrocarbons that all contain a similar number of carbon atoms, so have similar boiling points.

Question 19

What properties do short hydrocarbons have?

Answer 19

Low boiling point (volatile)
Easy to light and burn well (flammable)
Weak intermolecular forces

Question 20

What properties do large hydrocarbons have?

Answer 20

High boiling point
Hard to light
Viscous or thick
Strong intermolecular forces

Question 21

What is meant by homologous series?

Answer 21

Series of similar carbon and hydrogen molecules with different numbers of atoms

Question 22

Why do we crack long molecules?

Answer 22

Cracking is a process used to break these large hydrocarbons down into small molecules so that we can use them as fuels.

Question 23

What is the problems with carbon dioxide?

Answer 23

Carbon dioxide from burning fuels causes global warming, a process capable of changing the world’s climate significantly.

Question 24

What is the problems with carbon monoxide?

Answer 24

Increased levels of carbon monoxide reduce the amount of oxygen carried by haemoglobin around the body in red blood cells. The result is that vital organs, such as the brain, nervous tissues and the heart, do not receive enough oxygen to work properly

Question 25

What is the problem with particulates?

Answer 25

Larger particles are generally filtered in the nose and throat via cilia and mucus, but particulate matter smaller than about 10 micrometers, can settle in the bronchi and lungs and cause health problems.

Question 26

What can alkenes be used for?

Answer 26

To make polymers and other useful chemicals

Question 27

What is the method of cracking?

Answer 27

1) cracking is a thermal decomposition reaction- breaking molecules down by heating them
2) the first step is to heat long-chain hydrocarbons to vaporise them (turn them into a gas)
3) then the vapour is passed over a hot powdered aluminium oxide catalyst
4) the long-chain molecules split apart on the surface of the specks of catalyst- this is catalytic cracking

Question 28

How do you test for alkenes?

Answer 28

With Bromine water 💦:
When orange 🍊 bromine water is added to an alkane, no reaction will happen and it’ll stay bright orange
If it’s added to an alkene the bromine reacts with the alkene to make a colourless compound.

Question 29

How do you test for water vapour?

Answer 29

Cobalt chloride paper turned blue to pink when tested for water vapour

Question 30

How do you test for carbon dioxide?

Answer 30

Limewater turned cloudy when tested for carbon dioxide

Question 31

What is flammability?

Answer 31

How easy a substance ignites (sets on fire)

Question 32

What is viscosity?

Answer 32

How thick a liquid is

Question 33

What is boiling point

Answer 33

Liquid to gas

Question 34

What is volatility?

Answer 34

How easy a liquid turns into a gas

Question 35

Does boiling point increase or decrease with chain length?

Answer 35

Increases due to the increased number of intermolecular forces between molecules as the chain gets longer

Question 36

Does viscosity increase or decrease with chain length?

Answer 36

Increases, long chain alkanes are very thick and gloopy

Question 37

Does flammability and volatility increase or decrease with chain length?

Answer 37

The alkanes get less flammable as you increase the number of carbons