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Organic Chemistry Flashcards

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1
Q

What are hydrocarbons?

A

Molecules made up of hydrogen and carbon atoms ONLY.

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2
Q

What is the general formula for the homologous series of alkanes?

A

Cn H2n+2

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3
Q

Meth

A

One carbon

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4
Q

Eth

A

Two carbons

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5
Q

Prop

A

Three carbons

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6
Q

But

A

Four carbons

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7
Q

Pent

A

Five carbons

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8
Q

What ending signifies an alkane molecule?

A

ane

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9
Q

What are the first four members of the alkanes?

A

-methane
-ethane
-propane
-butane

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10
Q

How can alkanes be represented?

A

Using formulae e.g. C₂H₆

or using a displayed formula.

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11
Q

What do some properties of hydrocarbons depend on?

A

The size of their molecules.

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12
Q

What does the properties of different hydrocarbons influence?

A

How the hydrocarbons are used as fuels.

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13
Q

How does boiling point change with increasing molecular size and why?

A

The larger the molecules the higher the boiling point because the intermolecular forces between molecules are stronger and so require more energy to overcome.

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14
Q

How does viscosity change with increasing molecular size?

A

The larger the molecules the more viscous the hydrocarbon (i.e. the more gloopy/less runny).

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15
Q

How does flammability change with decreasing molecular size?

A

The smaller the molecules, the more flammable the hydrocarbon is (i.e. its easier to ignite).

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16
Q

Hydrocarbons with large molecules are often referred to as what?

A

Long-chain hydrocarbons

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17
Q

Hydrocarbons with small molecules are often referred to as what?

A

Short-chain hydrocarbons

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18
Q

What type of fuels are short-chain hydrocarbons often used as?

A

‘Bottled gases’.

Because they have lower boiling points they can be stored under pressure as liquids in bottles.

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19
Q

What is a homologous series?

A

A group of organic compounds that have similar chemical properties, due to them having the same general formula/functional group.

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20
Q

Isomers

A

Molecules made of the same atoms but are arranged in different ways.

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21
Q

What are alkanes?

A

The simplest type of hydrocarbon where each carbon atom forms FOUR SINGLE covalent bonds.

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22
Q

Saturated compound (for understanding)

A

One which contains the maximum possible number of hydrogen atoms bonded to its carbon atoms, with no carbon-carbon double or triple bonds present.

basically only single bonds present!

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23
Q

What is crude oil?

A

Crude oil is a finite resource found in rocks.

It is a mixture of a very large number of compounds.

Most of the compounds in crude oil are hydrocarbons, most of which are alkanes.

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24
Q

How is crude oil formed?

A

Crude oil is formed from the remains of an ancient biomass consisting mainly of plankton that was buried in mud.

Over millions of years - with high temperature and pressure - the remains turn to crude oil (which can be drilled up from the rocks where it’s found).

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25
Q

How is crude oil separated into fractions?

A

Fractional Distillation

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26
Q

Describe and explain how crude oil is separated into fractions by fractional distillation.

A

Crude oil is heated to vaporise the hydrocarbons and they are fed into the bottom of a fractionating column.

The temperature of the column decreases from bottom to top so the fractions condense at different heights.

This is because they have different boiling points.

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27
Q

What are fractions? (chemistry)

A

Groups of hydrocarbons with a similar number of carbon atoms and therefore similar melting and boiling points.

28
Q

What can fractions be processed to produced?

A

Fuels (e.g. for transport) and feedstock for the petrochemical industry.

29
Q

Give examples of fuels we depend on for our modern lifestyle (highest to lowest boiling point = bottom to top of fractionating column).

A

heavy fuel oil, diesel oil, kerosene, petrol/gasoline, liquefied petroleum gases (LPG)

30
Q

What is gasoline/petrol used for?

A

Fuel in car engines

31
Q

What is kerosene used for?

A

Aircraft fuel

32
Q

Feedstock

A

A raw material used to provide reactants for an industrial reaction.

(Used to make new compounds for use in things such as polymers, solvents, lubricants, and detergents.)

33
Q

Why is there such a vast array of natural and synthetic carbon compounds?

A

Sue to the ability of carbon atoms to form families of similar compounds. (homologous series)

34
Q

Petrochemical

A

A substance made from crude oil, via chemical reactions.

35
Q

Feedstocks vs petrochemicals

A

The different hydrocarbons in crude oil are all feedstocks but the things we make from the different hydrocarbons (polymers, lubricants, etc.) are all petrochemicals.

36
Q

What does the combustion of hydrocarbon fuels release?

A

Energy

37
Q

What happens to carbon and hydrogen in the (hydrocarbon) fuels during combustion?

A

They are oxidised because they gain oxygen.

38
Q

What are the products of the complete combustion of a hydrocarbon?

A

Carbon Dioxide + Water

(Water is in the gaseous form, aka water vapour).

39
Q

Students should be able to write balanced equations for the complete combustion of hydrocarbons…

A

…with a given formula.

40
Q

Complete combustion

A

Oxygen burns fully (as there’s an unlimited supply).

41
Q

How do we test for carbon dioxide (product of complete combustion)?

A

Bubble the CO₂ gas through limewater.

For a positive result, the limewater turns cloudy.

42
Q

How do we test for water (product of complete combustion)?

A

Add anhydrous copper sulfate powder.

For a positive result, the crystals will go from white to blue as the anhydrous copper sulfate goes to hydrated copper sulfate. (CuSO₄·5H₂O)

Alternatively use anhydrous cobalt chloride (blue to pink when hydrated).

43
Q

When does incomplete combustion occur?

A

When there’s a limited supply of oxygen.

44
Q

What are the products of incomplete combustion?

A

Carbon monoxide + Carbon + H₂O

45
Q

Why is incomplete combustion bad?

A

-Not much energy is given out

-Carbon monoxide is a toxic gas: it binds to haemoglobin instead of oxygen leading to unconsciousness and death

46
Q

Are longer or shorter hydrocarbons more useful? Why?

A

Short- chain hydrocarbons have lower boiling points so are more flammable and therefore make better fuels. They are in high demand.

Long-chain hydrocarbons are more viscous, forming thick gloopy liquids like tar which aren’t as useful.

47
Q

Why are hydrocarbons used as fuels?

A

A large amount of energy is released when they combust completely.

48
Q

Which reactants are oxidised (gain oxygen) during complete combustion?

A

Both hydrogen and carbon from the hydrocarbon.

49
Q

What is cracking?

A

The breaking down of long-chain hydrocarbons into smaller ones.

50
Q

What are the products of cracking?

A

A smaller alkane and an alkene.

51
Q

What are some of the products of cracking useful as?

A

Fuels e.g. petrol for cars and kerosene for planes.

52
Q

What type of reaction is cracking?

A

It is a type of thermal decomposition because molecules are broken down by heating them.

53
Q

Hydrocarbons can be broken down (________) to produce _______, more _______ molecules

A

cracked
smaller
useful

54
Q

Explain why compounds with the highest boiling points are found at the bottom of the fractionating column.

A

They have the longest molecules and therefore the strongest intermolecular forces.

55
Q

Why is cracking needed?

A

To meet the high demand for more short-chain hydrocarbons such as petrol, which are useful as fuels.

56
Q

Describe the conditions used for catalytic cracking.

A

-High temperatures
-A catalyst

57
Q

Describe the conditions used for steam cracking.

A

-High temperatures
-Steam.

58
Q

How can cracking be done?

A

By various methods including catalytic cracking and steam cracking.

59
Q

Are alkanes or alkenes more reactive?

A

Alkenes, hence they react with bromine water.

60
Q

What is the test for an alkene?

A

Bromine water is used to test for an alkene product.

For a positive result, the solution will go from orange to colourless.

61
Q

What is the colour change when bromine water reacts with an alkene?

A

Orange to Colourless (if the hydrocarbon is indeed unsaturated).

62
Q

Saturated

A

Contains only single bonds.

63
Q

Unsaturated

A

Can contain (Carbon–Carbon) double bonds.

64
Q

Practice some…

A

cracking equations!!!

64
Q

Explain how modern life depends on the uses of hydrocarbons.

A

Petrol is an example of an alkane in high demand in modern life for its use as a fuel in car engines.

Chemistry (13 decks)

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