Unit 10 - Organic Chemsitry

Question 1

What is crude oil

Answer 1

Crude oil is a mixture of hydrocarbons

Question 2

Describe how the industrial processes of fractional distillation separates crude oil into fractions

Answer 2

Because they have different boiling points, the substances in crude oil can be separated using fractional distillation.
The crude oil is evaporated and it’s vapours are allowed to condense a different temperatures in the fractioning column.
Each fraction contains a hydrocarbon molecules with a similar number of carbon atoms

Question 3

What are the main fractions obtained from crude oil

Answer 3

Refinery gases - bottled gas
gasoline - fuel for cars
Naphtha - making chemicals 
kerosene - aircraft fuel 
diesel - fuel for cars and buses
fuel oil - fuel for ships 
Residue / bitumen - for roads and roofs

Question 4

Describe the trend in boiling point and viscosity of the main fractionsA

Answer 4

As the boiling point increases so does the viscosity

Question 5

What is dangerous about the incomplete combustion a fuels

Answer 5

Incomplete combustion of fuels may produce carbon monoxide

CO is poisonous because it reduces the capacity of the blood to carry oxygen

Question 6

How are nitrogen oxides formed in car engines

Answer 6

The temperature reaches hi enough to allow much and oxygen from the air to react within the car engine

Question 7

How are the long chain hydrocarbons produced from the residue converted into shorter chain alkanes

Answer 7

The long train hard hydrocarbons are converted into useful alkanes and short-chain alkanes by catalytic cracking, using silica or alumina as the catalyst and a temperature in the range of 600 to 700°C to crack the long chains

Question 8

What are hydrocarbons

Answer 8

Hydrocarbons are compounds containing hydrogen and carbon only, joined conveniently

Question 9

What does it mean by a saturated hydrocarbon

Answer 9

Saturated means that all the covalent bond are single bonds

Question 10

What are Alkanes

Answer 10

Saturated hydrocarbons

General formula C(n)H(2n+2)

Question 11

What are isomers?

Answer 11

Substances with the same formula but different structure (arrangement of atoms)

Question 12

How and why do boiling points of alkenes change?

Answer 12

Boiling points increase as you go from one to another as larger molecules have stronger intermolecular forces.

Question 13

If a molecule is bigger it will have a….

Answer 13

Higher boiling point

Question 14

What is cracking?

Answer 14

The breaking down of large less useful oil fractions into smaller molecules

Question 15

What is catalytic cracking?

Answer 15

Cracking with the aid of a catalyst

Question 16

What is a monomer?

Answer 16

A small molecule which can join with itself to form a large molecules called a polymer

Question 17

What is addition polymerisation?

Answer 17

A process by which simple alkene molecules link together to form a large molecule with the same empirical formula

Question 18

Naming polymers after addition polymerisation (probably useful)

Answer 18

Ethene –> polythene
Propene –> polypropene
E.t.c

Question 19

What are alkenes

Answer 19

Hydrocarbons with a double bond

General formula H(n)C(2n)

Question 20

What are alkenes

Answer 20

Hydrocarbons with a double bond

General formula C(n)H(2n)

Question 21

Products of compels combustion of Alkanes

Answer 21

Water and CO2

Question 22

Products of incomplete combustion of Alkanes

Answer 22

Water and CO

Question 23

General formula for alkenes

Answer 23

CnH2n

Question 24

Describe the addition reaction of alkenes with bromine, including the bromine water test for alkenes

Answer 24

An alkene will make its double bond into a single bond, to bond to two bromines. Bromine is added to the molecule. The product made is colourless. When alkenes are put in bromine water it turns from brown to colourless (a good way of testing for alkenes.)
For example:
C2H4(g) + Br2 (aq) → C2H4Br2 (aq)

Question 25

Describe the manufacture of ethanol (from ethene)

Answer 25

Pass ethene and steam over a phosphoric acid catalyst at a temperature of about 300 degrees and a pressure of about 60-70atm

Question 26

Evaluate factors relevant to the choice of method you’d use to make ethanol

Answer 26

Fermentation:
Cane sugar widely avalible/ cheap/ renewable
Slow process
Impurities in the product
Done in batches

Hydrating (ethene and steam):
Crude oil (cracked to make ethene) expensive/ non-renewable
Fast process
Pure product
Continuous reaction

Question 27

Dehydration of ethanol to ethene using AlO

Answer 27

C2H5OH –> C2H4 + H2O
ethanol –> ethene + water

aluminium oxide is the catalyst for this reaction.

Question 28

How is an addition polymer formed?

Answer 28

By the joining up of many molecules called monomers

Question 29

What type of polymer is nylon ?

Answer 29

Nylon is a condensation polymer