1crude oil

Question 1

crude oil

Answer 1

mixture of hydrocarbons

Question 2

each fraction

Answer 2

consists of groups pf hydrocarbons of similar chain lengths

Question 3

each fraction in petroleum is separated in a process called

Answer 3

fractional distillation

Question 4

the molecules in each fraction have

Answer 4

similar boiling points and properties

Question 5

the size and length of each hydrocarbon molecule determines

Answer 5

in which fraction it will be separated into

Question 6

fractional distillation is carried out in a fractionating column which is

Answer 6

very hot at the bottom and cool at the top

Question 7

crude oil enters

Answer 7

the fractionating column and is heated so vapours rise

Question 8

boiling points in a fractionating column

Answer 8

low bp at the top, high at bottom

Question 9

fractions with smaller hydrocarbons are collected at

Answer 9

the top and the bigger ones at the bottom

Question 10

viscosity

Answer 10

This refers to the ease of flow of a liquid. High viscosity liquids are thick and flow less easily. If the number of carbon atoms increases, the attraction between the hydrocarbon molecules also increases which results in the liquid becoming more viscous with the increasing length of the hydrocarbon chain. The liquid flows less easily with increasing molecular mass

Question 11

colour

Answer 11

As carbon chain length increases the colour of the liquid gets darker as it gets thicker and more viscous

Question 12

mp/bp

Answer 12

As the molecules get larger, the intermolecular attraction becomes greater. So more heat is needed to separate the molecules. With increasing molecular size there is an increase in boiling point

Question 13

combustion of fossil fuels is

Answer 13

the major source of atmospheric pollution

Question 14

the burning of fossil fuels releases gases such as

Answer 14

carbon dioxide, carbon monoxide, oxides of nitrogen and oxides of sulfur as well as unburned hydrocarbons and carbon particulates

Question 15

a fuel is

Answer 15

a substance which releases energy in an exothermic reaction

Question 16

complete combustion occurs when

Answer 16

there is excess oxygen

Question 17

incomplete combustion occurs when there is

Answer 17

insufficient oxygen to burn

Question 18

carbon dioxide is

Answer 18

a toxic and odourless gas which can cause dizziness, loss of consciousness and eventually death

Question 19

nitrogen and nitrogen oxides are formed when

Answer 19

nitrogen and oxygen react in the high pressure and temperature conditions of internal combustion engines and blast furnaces

Question 20

exhaust gases contain

Answer 20

unburned hydrocarbons and carbon monoxide

Question 21

cars are fitted with

Answer 21

catalytic converters which form a part of their exhaust systems- their function is to render these exhaust gases harmless

Question 22

catalytic converters contain a series of

Answer 22

transition metal catalysts including platinum and rhodium,

Question 23

sulfur dioxide sources

Answer 23

combustion of fossil fuels- especially coal

Question 24

fossil fuels are often contaminated with

Answer 24

small amounts of sulfur impurities- when these contaminated fossil fuels are combusted, the sulfur in the fuels get oxidised to sulfur dioxide

Question 25

the sulfur dioxide produces from

Answer 25

the combustion of fossil fuels dissolves in rainwater droplets to form sulfuric acid

Question 26

nitrogen dioxide also contributes to

Answer 26

acid rain

Question 27

alkanes are

Answer 27

saturated compounds

Question 28

alkenes are

Answer 28

unsaturated compounds

Question 29

cracking is

Answer 29

converting long chain alkanes into short chain alkenes which are more useful

Question 30

kerosene and diesel oil are often cracked to

Answer 30

produce petrol

Question 31

methods of cracking

Answer 31

catalytic cracking and steam cracking

Question 32

catalytic cracking

Answer 32

Catalytic cracking involves heating the hydrocarbon molecules to around 470 – 550°C to vaporise them
The vapours then pass over a hot powdered catalyst of aluminium oxide
This process breaks covalent bonds in the molecules as they come into contact with the surface of the catalyst, causing thermal decomposition reactions
The molecules are broken up in a random way which produces a mixture of smaller alkanes and alkenes
Hydrogen and a higher proportion of alkenes are formed at higher temperatures and higher pressure

Question 33

why is cracking necessary

Answer 33

Crude oils vary considerably in their composition and some need more refining than others
Supply is how much of a particular fraction can be produced from refining the crude oil
Demand is how much customers want to buy
General the demand for certain fractions outstrips the supply so this is why cracking is necessary to convert surplus unwanted fractions into more useful ones
This is mostly larger, heavier fractions that are cracked into smaller lighter fractions

Question 34

Answer 34

Question 35

cracking is used to

Answer 35

convert long chain alkane molecules into short chain molecules which are more useful

Question 36

what is produced during cracking

Answer 36

small alkenes and hydrogen

Question 37

kerosene and diesel oil are often

Answer 37

cracked to produce petrol, other alkenes and hydrogen

Question 38

methods of cracking

Answer 38

catalytic cracking and steam cracking