CC16 - fuels

Question 1

what is a hydrocarbon

Answer 1

a compound of only hydrogen and carbon

Question 2

what is crude oil

Answer 2

natural resource a complex mixture of hydrocarbons
an important source of fuel and feedstock for petrochemical industry

Question 3

why is crude oil a finite resource

Answer 3

takes so long to make it is being used faster than made and will one day run out

Question 4

where does crude oil come from

Answer 4

formed underground at high temp and pressure over millions of years from plant and animal remains

Question 5

what is crude oil made up of

Answer 5

lots of different hydrocarbons of different lengths

Question 6

what can crude oil be separated into

Answer 6

fractions: simpler more useful mixtures containing hydrocarbons of similar lengths

Question 7

what are the fractions of crude oil

Answer 7

• gases
• petrol
• kerosene
• diesel
• fuel oil
• bitumen

Question 8

what is feedstock

Answer 8

raw materials

Question 9

how are the fractions in crude oil separated

Answer 9

fractional distillation:
shorter hydrocarbons have lower boiling separate near top of column where it is cooler and vise versa

Question 10

what are gases used for

Answer 10

domestic heating and cooking

Question 11

what is petrol used for

Answer 11

fuel in cars

Question 12

what is kerosene used for

Answer 12

fuel in planes

Question 13

what is diesel used for

Answer 13

fuel in some cars and larger vehicles such as trains

Question 14

what is fuel oil used for

Answer 14

fuel for large ships and some powerstations

Question 15

what is bitumen used for

Answer 15

surface roads and roofs

Question 16

what do the physical properties of crude oil depend on

Answer 16

how big the hydrocarbons in the fraction are

Question 17

how does boiling point change in fractions of hydrocarbons

Answer 17

increases as hydrocarbon chains get longer. shorter chain have weaker intermolecular forces of attraction

Question 18

how does ignition change in fractions of hydrocarbons

Answer 18

shorter chain hydrocarbons ignite easier

Question 19

how does viscosity change in fractions of hydrocarbons

Answer 19

longer chain hydrocarbons are more viscous

Question 20

how does colour change in fractions of hydrocarbons

Answer 20

longer chain hydrocarbons tend to be darker in colour

Question 21

how many bonds does a carbon atom form

Answer 21

4

Question 22

how many bonds does a hydrogen atom form

Answer 22

1

Question 23

what is an alkane

Answer 23

single covalent bond between all carbon atoms (saturated)
formula: C(n)C(2n+2)

Question 24

what is an alkene

Answer 24

have atleast one double covalent bond between carbon atoms (unsaturated)
formula: C(n)H(2n)

Question 25

what is a homologous series

Answer 25

a series of compound that:
- same general formula
- differ by CH2 of neighbouring compounds
- similar chemical properties
- gradual variation of physical properties

Question 26

what do oil fractions mostly contain

Answer 26

alkanes

Question 27

what is complete combustion

Answer 27

reaction between hydrocarbon and O2
when theres a plentiful supply of oxygen
is an exothermic reaction

Question 28

general formula for complete combustion

Answer 28

hydrocarbon + oxygen —-> carbon dioxide + water

Question 29

when does incomplete combustion occur

Answer 29

limited supply of oxygen (in appliances such as boilers)

Question 30

products of incomplete combustion

Answer 30

water, carbon dioxide, carbon monoxide, carbon (less O2)

Question 31

problems of carbon monoxide

Answer 31

• colourless, odorless gas
• binds to haemoglobin in RBC limiting O2 in blood stream
• result in fainting, coma, even death

Question 32

problems of carbon (incomplete combustion)

Answer 32

soot: blacken buildings, clog pipes, reduce air quality, cause breathing problems

Question 33

acid rain

Answer 33

• sulfur impurities in hydrocarbons oxidise and form sulfur dioxide when burnt
• sulfur dioxide dissolves in water in clouds sulfuric acid that falls as acid rain

Question 34

effects of acid rain

Answer 34

• corrodes metal and limestone weakening buildings
• damages crops, plants and trees
• kills fish (rivers and lakes too acidic to survive) and insects

Question 35

oxides of nitrogen

Answer 35

• nitrogen and O2 from air react under high temperatures in car engines

Question 36

effects of oxides of nitrogen

Answer 36

harmful pollutants
cause photochemical smog
air pollution: difficulty breathing, headaches

Question 37

advantages of using hydrogen as a fuel

Answer 37

• only waste product is water
• renewable (obtained from water)

Question 38

disadvantages of using hydrogen as a fuel

Answer 38

• hard to store
• not widley avaliable
• expensive to manufacture
• special, expensive engine required

Question 39

what is cracking

Answer 39

taking a long chain hydrocarbon (alkane) and breaking it down into shorter more useful hydrocarbons (alkane and alkene)

Question 40

what are the two types of cracking

Answer 40

thermal and catalytic

Question 41

what is catalytic cracking

Answer 41

• use high temp and a catalyst
• catalyst speeds up the reaction
• covalent bonds break and reform

Question 42

why are alkenes useful

Answer 42

• used to make polymers
• used as a starting material for useful chemicals
• useful as feedstock for petrochemical industry

Question 43

thermal cracking

Answer 43

• uses high temperatures of up to 750°c

Question 44

reasons for cracking

Answer 44

• shorter chain hydrocarbons more useful and in higher demand but in less supply
• longer chain hydrocarbon that there are more of in less demand can be cracked to meet supply of shorter chain hydrocarbons