Organic chemistry

Question 1

What does fractional distillation mean?

Answer 1

To seperate a mixture by it’s boiling points?

Question 2

How does fractional distillation separate crude oil?

Answer 2

By the different boiling points of the hydrocarbons in the mixture?

Question 3

What are hydrocarbons?

Answer 3

A compound made ONLY of hydrogen and carbon atoms

Question 4

what is crude oil?

Answer 4

a mixture of compounds containing the biomass. A finite resource

Question 5

what are alkanes?

Answer 5

Saturated (only has single bonds with carbons) hydrocarbons with the formula
CnH2n+2

Question 6

what is a homologous series?

Answer 6

series of compounds with the same general formula

Question 7

Describe how fractional distillation takes place

Answer 7

Crude oil is heated to it’s boiling point of 350oc
The crude oil vaporises
The column is hotter at the bottom and cooler at the top
The hydrocarbons rise up and condense once they reach there boiling point
Large hydrocarbons are collected at the bottom as they have bigger boiling point
Small hydrocarbons are collected at the top as they have a smaller boiling point

Question 8

Describe small chain hydrocarbons?

Answer 8

Highly flammable and also low viscosity and more volatile (evaporate easier)

Question 9

Describe large chain hydrocarbons

Answer 9

Not very good fuel and high viscosity

Question 10

Describe combustion of hydrocarbons?

Answer 10

Hydrocarbon + oxygen = carbon dioxide + water
The hydrogen and carbon are being oxidised
It releases lots of energy in the process so it is considered a exothermic reaction
Incomplete combustion produces water and carbon monoxide

Question 11

Describe the physical properties of alkanes

Answer 11

As they get bigger, larger boiling point and more viscosity
the smaller means they are more flammable and can be used as a fuel
when used as a fuel it is called combustion

Question 12

What is cracking?

Answer 12

A thermal decomposition reaction ( Using heat to break down a hydrocarbon)

Question 13

Equation for cracking?

Answer 13

Long alkane = short alkane + alkene

Question 14

Describe catalytic cracking

Answer 14

1. The hydrocarbon is vaporised ( heated until a gas)
2. The gas is then combined with a catalyst (powdered alumium oxide)
3. as the hydrocarbon comes into contact with the catalyst it splits apart

Question 15

Describe steam cracking

Answer 15

1. The hydrocarbon is vaporised
2. It is then combined with steam
3. this causes the hydrocarbon to split into two

Question 16

What are the products of cracking used for?

Answer 16

short chain alkanes - used for fuel
alkenes- petrochemical feedstock, polymers

Question 17

Test of alkenes

Answer 17

1. more reactive then alkanes - can react with bromine
   solution of alkenes + bromine water will go from orange to colourless

Question 18

Describe the combustion of alkenes

Answer 18

They burn with a smoky flame due to incomplete combustion

Question 19

How does alkenes c=c bond allow them to undergo addition reaction?

Answer 19

There unsaturated bond can open up allowing the hydrocarbon to bond to other molecules

Question 20

Describe hydrogenation

Answer 20

Alkene + hydrogen +(catalyst)= alkane
The C=C bond will break allowing the H2 to combine
allowing it to become saturated

Question 21

Def of hydration

Answer 21

Alkene + water (vapor due to the presence of high temperature and a catalyst) = alcohol

The double bond of the alkene breaks allowing the H and OH to combine to the alcohol
OH becomes the function group of the alcohol

Question 22

What is concentrated fractional distilation?

Answer 22

When making alcohols
The alcohol is still needs to be sperated from it’s alkene and water vapor
1. condense the gas- the alkene will stay as a gas while the alcohol and water stay as a liquid
2. Use fractional distilation to seperate the alcohol and water
3. The ethanol will boil first and rise to cool and condense and be collected

Question 23

Reaction of alkenes with halogens?

Answer 23

Halogenoalkane- e.g ethene + Br2 = dibromoethane

Halgoens are diatomic so create diatomic products

Question 24

state the charcteristics of
methanol
ethanol
propanol
butanol

Answer 24

Dissolve in water to form a neutral solution
react with sodium to produce hydrogen
Burn in oxygen
react with carboxylic acids
to produce esters

Question 25

What is the general formula for alcohols?

Answer 25

Cn H2n+1

Question 26

Properties of alcohols

Answer 26

Flammable
soluble
and can be oxidised to become carboxylic acids

Question 27

Uses of alcohols

Answer 27

As a fuel as they are very flammable and release a lot of energy
Often used as a solvent as alcohol can absorb things water cannot- the bigger the alcohol the less soluble it is

Question 28

Ethanol can be made by fermentation
what are the conditions required?

Answer 28

A catalyst - sugar dissolved in water and yeast
Anerobic conditions so no oxygen can get in
warm temperature 25-30oC

Question 29

Advantages of making ethanol from hydration of ethene?

Answer 29

Ethene + steam = ethanol
100% atom economy
instant process
disadvantages
Requires lots of energy
crude oil is non renewable
contribution to global warming

Question 30

Advantages of making ethanol from fermentation

Answer 30

Absorbs the co2 even though it produces co2 so it is carbon neutral
renewable
disadvantages
must be kept in anerobic conditions
takes weeks to make and only has 15% atom economy

Question 31

what is the function group of carboxylic acids

Answer 31

-COOH

Question 32

State the characteristics of carboxylic acids

Answer 32

They can only partially ionise in water
react with metal carbonates to make salt + water+ co2
React with alcohols to create esters
react with metal to create hydrogen

Question 33

what are esters

Answer 33

A compound with the function group -COO- formed from a carboxylic acid and alcohol in the presence of a catalyst

e.g ethanoic acid + ethanol = ethyl ethanoate + water

Question 34

Name two naturally occuring polymers from glucose

Answer 34

Starch and cellulose

Question 35

Describe the shape and structure of the polymer DNA

Answer 35

Double helix
4 different nucleotides present (e.g thymine, adenine)
Two polymer chains