Alkanes

Question 1

What does fractional distillation of crude oil do?

Answer 1

Separate hydrocarbons into fractions

Question 2

What two physical processes are involved in fractional distillation

Answer 2

Boiling and condensation (as fractions leave column as liquids)

Question 3

What is a fraction

Answer 3

A mixture of hydrocarbons with similar boiling points

Question 4

What do C1 to C4 carbons make

Answer 4

Liquefied petroleum gas

Question 5

What do C5 to C9 carbons make

Answer 5

Chemicals

Question 6

What do C5 to C10 carbons make

Answer 6

Petrol for vehicles

Question 7

What do C10 to C16 carbons make

Answer 7

Jet fuel and paraffin

Question 8

What do C14 to C20 carbons make

Answer 8

Diesel fuels

Question 9

What do C20 to C50 carbons make

Answer 9

Waxes, lubricants and polishes

Question 10

What do C20 to C70 carbons make

Answer 10

Fuels for ships, factories and central heating

Question 11

What do >C70 carbons make

Answer 11

Bitumen for roads and roofing

Question 12

Describe fractional distillation

Answer 12

Hydrocarbons separates due to different boiling points
Boiling point depends on C Chain length
Cooler at top of column
Higher boiling point chains evaporated at the bottom of the column

Question 13

Define saturated hydrocarbons

Answer 13

Contains single bonds ONLY

Question 14

Define unsaturated

Answer 14

Contains at least one C=C double bond

Question 15

Define hydrocarbon

Answer 15

Contains hydrogen and carbon only

Question 16

Why do we crack long chain alkanes?

Answer 16

Shorter chain alkanes are in higher demand

Question 17

Give the conditions of thermal cracking

Answer 17

High temperature- 1000K
High pressure- 7000kPa
Free radical intermediates

Question 18

What does thermal cracking produce

Answer 18

High percentage of alkenes and straight chain alkanes

Question 19

Give the conditions of catalytic cracking

Answer 19

High temperature- 720K
Moderate pressure - 100-500kPa
Uses catalysts eg zeolite crystals
Carbocations intermediates

Question 20

What is catalytic cracking used to produce

Answer 20

Motor fuels
Aromatic hydrocarbons
Cycloalkanes

Question 21

What are the products of the complete combustion of alkanes

Answer 21

H20 and CO2

Question 22

Products of the incomplete combustion of hydrocarbons

Answer 22

CO and water

Or

C and water

Question 23

Why is

a) carbon monoxide
b) Carbon particulates
c) CO2

a pollutant

Answer 23

a) It is poisonous
b) exacerbates asthma
c) green house gas

Question 24

Why are 
Nitrogen oxides
Sulphur dioxide
Water vapour 
Pollutants?

Answer 24

NO and NO2 form nitric acid with water and cause acid rain

SO2 forms H2SO4, causing acid rain

Water vapour is a greenhouse gas

Question 25

How is NO and NO2 formed

Answer 25

N2 and O2 react together when a spark is generated in a hot engine

Question 26

How is sulphur removed? Give the equation

Answer 26

Glue gas desulphurisation: It is neutralised by CaO or CaCO3 CaO + SO2 —> CaSO3 This prevents acid rain

Question 27

Why is CaO used in desulphurisation

Answer 27

It is a base and SO2 is acidic

Question 28

Why are catalytic converters fitted to cars

Answer 28

Reduce amount of CO, C, and NO produces

Question 29

Equation for formation of NO

Answer 29

N2 + O2 —> NO2

Question 30

Describe the catalyst used in catalytic converters

Answer 30

Honeycomb structure to increase surface area and improve cost effectiveness Made of ceramic material to withstand high temperatures Honeycomb is coated in catalyst (eg Platinum, palladium or rhodium)

Question 31

What happens to the pollutant gases as they pass over the catalyst in a converter?

Answer 31

They are adsorbed on the surface of the catalyst (held to the catalyst’s surface)

Question 32

What is the equation for the conversion of CO and NO in a catalytic converter

Answer 32

2CO + 2NO —> 2CO2 + N2

Question 33

What is the equation for C8H18 and NO in a catalytic converter?

Answer 33

C8H18 + 25NO —> 8CO2 + 12.5N2 +9H2O

Question 34

Conditions for catalytic cracking What does it produce

Answer 34

High temperature Moderate pressure Zeolite catalyst Branched and cyclic alkanes, Aromatics Motor fuels

Question 35

How is the exhaust gas octane removed

Answer 35

React with NO in a catalytic converter to produce CO2, N2 and H2O

Question 36

Reaction of octane and NO

Answer 36

C8H18 + NO —-> CO2 + N2 + H2O