Alkanes

Question 1

What is petroleum?

Answer 1

Mixture consisting of mainly alkane hydrocarbons that can be separated by fractional distillation

Question 2

What is the method of fractional distillation?

Answer 2

1) Crude oil vaporised at 350°C
2) Vapourised curde oil passed into fractionating column which has a negative temperature gradient
3) As vapour rises it cools
4) Molecules condense at different temperatres, so drawn off at different levels in the column

Question 3

What is the residue(1st bottom) fraction? what are the uses?

Answer 3

Fuel oil: Ships and power stations
Wax: Candles and Lubrication
Bitumen: Roofing and road surfacing

Question 4

What is the fraction that is drawn off at 340°C (2nd)? What are the uses?

Answer 4

Mineral oil: lubrication

Question 5

What is the fraction that is drawn off at 250°C (3rd)? What are the uses?

Answer 5

Gas oil(diesel): Diesel fuel, Central heating fuel

Question 6

What is the fraction that is drawn off at 180°C (4th)? What are the uses?

Answer 6

Kerosine(paraffin): Jet fuel, Petrochemicals, central heating fuel

Question 7

What is the fraction that is drawn off at 110°C (5th)? What are the uses?

Answer 7

Naphtha: processed to make petrochemicals

Question 8

What is the fraction that is drawn off at 40°C (6th)? What are the uses?

Answer 8

Petrol: cars

Question 9

What is the top fraction that remains a gas used for?

Answer 9

Liquified petroleum gas, camping gas

Question 10

What does thermal cracking involve?

Answer 10

• High temperature
• Produces high percentage of alkenes which can be used go make plastics

Question 11

What does catalytic cracking involve?

Answer 11

• Zeolite catalyst
• Slight pressure and high temperature (significantly less than thermal cracking)
• Mainly produces aromatic hydrocarbons and motor carbons

Question 12

What does the formation of soot in incomplete combustion lead to?

Answer 12

Can cause breathing problems and build up in engines, damaging them

Question 13

What does the formation of carbon monoxide in incomplete combustion lead to?

Answer 13

Poisonous as it binds to haemoglobin more readily, and blocks oxygen

Question 14

What do catalytic converters involve, and what do they do?

Answer 14

Palladium, platinum, or rhodium catalyst that has a honeycomb structure, increasing SA - heterogenous catalyst
Removes unburnt hydrocarbons, oxides of nitrogen, and carbon monoxide from exhausts

Question 15

What are the conditions needed for oxides of nitrogen to form?

Answer 15

Spark
High temperature

Question 16

What are the dangers of unburnt hydrocarbons and oxides of nitrogen?

Answer 16

React in presence of sunlight, forming ground level ozone, which causes smog. Irritates eyes, aggravates respiratory problems

Question 17

What is the danger of SO2

Answer 17

Dissolves in moisture which makes sulfuric acid, causing acid rain. This damages vegetation, corrodes buildings and statues and kills marine wildlife

Question 18

How can SO2 be removed from flue gases?

Answer 18

Using CaO or CaCO3. Powdered CaO or CaCO3 mixed with water, making an alkaline slurry.
Flue gases mixed with this, acidic sulfur dioxide reacts with them, causing them to form a salt(calcium sulfide)

Question 19

Stages of chlorination of alkanes

Answer 19

Stage 1: Initiation - UV breaks Cl-Cl bond to make free radicals
Stage 2: Propagation - Cl radical reacts with methane making a methyl radical which attacks a Cl2 molecule forming CH3Cl
Stage 3: Termination - Free radicals join

Question 20

What happens in Chlorine is in excess?

Answer 20

Cl free radicals attack the chloromethane, producing dichloromethane onwards…

Question 21

Nucleophiles

Answer 21

Electron pair donors

Question 22

Nucleophiles that attack halogenolkanes

Answer 22

OH⁻ CN⁻ NH3

Question 23

Halogenoalkane with hydroxide conditions:

Answer 23

Heat under reflux in aqueous solution

Question 24

Halogenoalkane with cyanide conditions:

Answer 24

Reflux with ethanolic potassium cyanide

Question 25

Halogenoalkane with ammonia conditions:

Answer 25

Heated with ethanolic ammonia