C9 Crude Oils and Fuels

Question 1

how is crude oil formed?

Answer 1

over millions of years
as remains of ancient sea animals and plants are pressured under rocks
at a high temperature
without oxygen.

Question 2

what compounds is crude oil made of?

Answer 2

mostly made of hydrocarbon compounds
as well as mixtures of other carbon compounds

Question 3

formula of an alkane

Answer 3

CnH(2n+2)

Question 4

describe bonding in an alkane

Answer 4

saturated hydrocarbon
- SINGLE covalent bond between all carbon atoms: saturated,
- each molecule contains as many hydrogen atoms as possible.

Question 5

alkane/alkene prefixes

Answer 5

meth (1 carbon atom)
eth (2 carbo atoms)
prop (3 carbon atoms)
but (4 carbon atoms)

Question 6

which types of hydrocarbon are most useful?
why?

Answer 6

short-chain
ignite more easily, burn well, with non-smoky flame

Question 7

compare the properties of short and long-chain hydrocarbons

Answer 7

short-chain
- very flammable: less smoky flame,
- low viscosity (thin, runny),
- highly volatile,
- low boiling point.

long-chain
- less flammable: smoky flame,
- high viscosity (thick),
- lower volatility,
- higher boiling point.

Question 8

what does it mean for something to be highly volatile?

Answer 8

it has a strong tendency to become a gas.

Question 9

what are products collected from the fractional distillation of crude oil used for?

Answer 9

petrol, kerosene, diesel oil, petroleum gas

Question 10

what are the lighter fractions from fractional distillation of crude oil used for?

Answer 10

fuel

Question 11

word equation for complete combustion of hydrocarbons

Answer 11

hydrocarbon + oxygen -> carbon dioxide + water

Question 12

product of incomplete combustion

Answer 12

carbon monoxide

Question 13

what is cracking?

Answer 13

breaking long-chain hydrocarbons into short-chained, more useful ones

Question 14

describe the process of cracking hydrocarbons

Answer 14

1. heat them so that they vapourise,
2. either pass the vapour over a hot catalyst, or mix with steam and heat to a hotter temp.

Question 15

what type of chemical reaction happens during cracking?

Answer 15

thermal decomposition reactions
when large molecules split into smaller, more useful ones

Question 16

formula of alkene

Answer 16

CnH2n

Question 17

bonding in an alkene

Answer 17

unsaturated
- at least one DOUBLE bond between carbon atoms

Question 18

compare the properties of alkenes and alkanes

Answer 18

• alkenes generally more reactive,
• both burn in air but alkanes burn better,
  (alkenes tend to combust incompletely, producing a yellow, smoky flame)
• alkenes react with orange bromine water and turn it colourless, whereas alkanes do not,

Question 19

which hydrocarbons can and cannot participate in addition reactions?

Answer 19

alkenes can endure addition reactions,
alkanes cannot because all of their carbon atoms are already covalently bonded to a hydrogen atoms

Question 20

what does cracking produce?

Answer 20

produces alkanes and alkenes

Question 21

test for alkene

Answer 21

turns orange bromine water colourless