Organic chemistry

Question 1

What are hydrocarbons?

Answer 1

a compound that is made up from molecules of hydrogen and carbon atoms only

Question 2

What is crude oil?

Answer 2

• mixture of a very large number of compounds
• finite resource found in rocks
• fossil fuel

Question 3

How is crude oil formed?

Answer 3

• organic matter (plankton) is buried under sediment
• buried for millions of years
• subject to high temperature and pressures

Question 4

What are alkanes?

Answer 4

the simplest type of hydrocarbon you can get

Question 5

What is the general formula for alkanes?

Answer 5

Cn H2n+2

Question 6

What type of compound are alkanes and what does it mean?

Answer 6

saturated - contains only single bonds

Question 7

What are the first 4 alkanes?

Answer 7

Methane - Monkeys
Ethane - Eat
Propane - Peanut
Butane - Butter

Question 8

What type of series are alkanes?

Answer 8

homologous series - a group of organic compounds that react in a similar way

Question 9

What happens to the viscosity the longer the molecules?

Answer 9

• increases as the number of carbons increases
• stronger forces between molecules mean they can flow less easily

Question 10

What happens to the boiling point the longer the molecules?

Answer 10

• as the number of carbon increases, the boiling point increases
• larger molecules have more electrons
• so have stronger intermolecular forces that take more energy to break

Question 11

What happens to the flammability the longer the molecules?

Answer 11

fewer carbons, more flammable

Question 12

What is the difference between flames of shorter and longer chains?

Answer 12

shorter chain - clearer flame
longer chain - sooty flame

Question 13

What is combustion?

Answer 13

Reaction between a fuel and oxygen that releases energy i.e exothermic

Question 14

What does the complete combustion of a hydrocarbon produce?

Answer 14

carbon dioxide and water

Question 15

Why are hydrocarbons used as fuels?

Answer 15

they release large amounts of energy when they combust completely

Question 16

How can crude oil be split into separate groups of hydrocarbons?

Answer 16

Fractional distillation

Question 17

What is the process of fractional distillation of crude oil?

Answer 17

• crude oil is heated until it vaporises
• the vapour goes into the fractioning column which is hotter at the bottom and cooler at the top
• vapour rise and condense at the part of the column which is at the temperature of their boiling point which is related to carbon chain length
• longer chain and larger molecules condense near the bottom and shorter chains and smaller molecules at the top

Question 18

What is the order of the fraction columns in fractional distillation starting from the bottom?

Answer 18

• bitumen (tarmac + roofing)
• heavy fuel oil (ships)
• lubricating oil
• diesel oil
• kerosene (jet fuel)
• naphtha (feedstock for other chemical purposes)
• petrol
• bottle gas (heating/cooking)

Question 19

Why is cracking used?

Answer 19

The demand for smaller hydrocarbons outweighs the supply, whereas the demand for larger hydrocarbons is far below the supply.

Short-chain hydrocarbons are flammable so make good fuels and are high in demand

Question 20

What is cracking?

Answer 20

Hydrocarbons can be broken down (cracked) to produce smaller, more useful molecules.

Question 21

What are the 2 types of cracking?

Answer 21

• steam cracking
• catalytic cracking

Question 22

What is catalytic cracking?

Answer 22

• high temperature (550°C) as the alkane must be a vapour
• The alkane vapours are passed over a catalyst (aluminium oxide, often from zeolite found in pottery)

Question 23

What is steam cracking?

Answer 23

• done at a high temperature (800°C),
• the alkane vapours are mixed with steam

Question 24

What are the products of cracking?

Answer 24

alkanes and another type of hydrocarbon called alkenes.

Question 25

What is an alkene?

Answer 25

an unsaturated hydrocarbon that contains a a carbon-carbon double bond and has the general formula CnH2n

Question 26

What's more reactive, an alkane or alkene?

Answer 26

alkene

Question 27

What is the test for the presence of an alkene?

Answer 27

Bromine water changes from orange to colourless

Question 28

What are the some of the products of cracking useful for?

Answer 28

There is a high demand for fuels with small molecules and so some of the products of cracking are useful as fuels.

Question 29

Why are alkene molecules unsaturated?

Answer 29

Alkene molecules are unsaturated because they contain two fewer hydrogen atoms than the alkane with the same number of carbon atoms.

Question 30

What does incomplete combustion of an alkene result in?

Answer 30

smoky yellow flame

Question 31

In what way do most alkenes react?

Answer 31

addition reactions

Question 32

What is hydrogenation?

Answer 32

Hydrogen can react with the double-bonded carbons to open up the double bond and from the equivalent saturated alkane

Question 33

What happens in hydration?

Answer 33

when alkenes react with steam (300C) in the presence of a phosphoric acid catalyst, water is added across the double bond and an alcohol is formed

Question 34

What happens in halogenation?

Answer 34

alkenes will also react in addition reactions with halogens such as bromine, chlorine and iodine. The molecules formed are saturated, with C=C carbons each becoming bonded to a halogen atom

Question 35

What is the functional group of alcohols?

Answer 35

OH-

Question 36

What are the first four members of a homologous series of alcohols?

Answer 36

- Methanol - ethanol - propanol - butanol

Question 37

What are the properties of the first 4 alcohol?

Answer 37

- the first 4 alcohols all dissolve completely in water to form neutral solutions (pH of exactly 7) as they don't ionise like carboxylic acids - reacts with sodium (gentle fizzing, sodium disappears, white solid) - alcohols are flammable so they burn in air to produce carbon dioxide and water - can be oxidised by reacting with oxygen to form carboxylic acids

Question 38

What are the uses of alcohols?

Answer 38

- drinks - solvents for perfumes and aftershave lotions - fuels

Question 39

What is fermentation?

Answer 39

Aqueous solutions of ethanol are produced when sugar solutions are fermented using yeast.

Question 40

What conditions are needed for the fermentation of sugar using yeast?

Answer 40

- temperature of around 37C - slightly acidic condition - under anaerobic conditions

Question 41

What is the functional group of carboxylic acids?

Answer 41

- COOH

Question 42

What are the first four members of a homologous series of carboxylic acids

Answer 42

- methanoic acid - ethanoic acid - propanoic acid - butanoic acid

Question 43

What happens when carboxylic acids react with carbonates?

Answer 43

produce carbon dioxide, a salt and water the salts formed end in 'anoate'

Question 44

What happens when carboxylic acids dissolved in water?

Answer 44

they can ionise and release H+ ions which are responsible for making the solution acidic

Question 45

What type of acids are carboxylic acids?

Answer 45

weak acids so carboxylic acids have a higher pH than aqueous solutions of strong acids with the same concentration

Question 46

What is the functional group of esters?

Answer 46

-COO-

Question 47

What are condensation polymers?

Answer 47

- involve monomers with 2 functional groups - when these type of monomers react they joining together, usually losing small molecules such as water, and so the reactions are called condensation reactions

Question 48

What are the properties of LDPE?

Answer 48

- flexible - unreactive - can be made into films - chains are branched which means the molecules are arranged randomly

Question 49

What are the uses of LDPE?

Answer 49

- carrier bags - bubble wrap

Question 50

What are the properties of HDPE?

Answer 50

- strong - flexible - resists shattering - resists chemical attack - less branching of the polymer chains, so the molecules line up much more closely

Question 51

What are the uses of HDPE?

Answer 51

- plastic bottles - pipes - buckets

Question 52

Describe amino acids

Answer 52

- have 2 different functional groups in a molecule - react by condensation polymerisation to produce polypetides

Question 53

What is DNA?

Answer 53

deoxyribonucleic acid

Question 54

What are DNA molecules made up of?

Answer 54

2 polymer chains, made from 4 different monomers called nucleotides in form of a double helix

Question 55

What are sugars?

Answer 55

small molecules that contain carbon, oxygen and hydrogen - can react together through polymerisation reactions to form polymers such as starch and cellulose