fractional distillation in a fractioning column // oil is heated to 350oC // heavier fractions with higher MP condense first and come off lower in the column // small come off at top
2 of 24
What are the non-vaporisable hydrocarbons called?
bitumen
3 of 24
Why do larger hydrocarbons have higher melting points?
more Van der Waal forces // larger surface area of contact so VdW stronger
4 of 24
what is a fuel?
release heat energy when burnt
5 of 24
describe the complete combustion of alkanes
highly exothermic// produces more energy when forming new bonds// produces water and co2
6 of 24
where are alkanes used?
used as fuels in industry, home and transport
7 of 24
what is the consequence of poor ventilation when an alkane is being burnt?
incomplete combustion can occur producing carbon monoxide
8 of 24
Describe the incomplete combustion of alkanes
1/2 oxygen (O2) produces CO
9 of 24
How is carbon monoxide toxic?
colour/odourless gas// binds with haemoglobin more readily that oxygen// suffocation
10 of 24
What is the formula for alkanes?
CnH2n+2
11 of 24
what are cycloalkanes?
ring shaped -2H
12 of 24
describe the shape and bond angle of alkanes
bond angle 109.5// tetrahedral // all bonding pairs repel equally
13 of 24
why are alkanes un-reactive?
C-C and C-H bonds are non-polar
14 of 24
Describe the intermolecular forces between hydrocarbons
Van der Waal's only
15 of 24
What is meant by the 'cracking' of hydrocarbons?
conversion of long chain H.carbons into smaller molecules by breakage of C-C bonds
16 of 24
Why are hydrocarbons cracked?
long chain H.carbons are not very useful// cracked to produce smaller more useful
17 of 24
What are the economic reasons behind cracking?
short chain H.carbons make petrol which is high in demand// supply demand for shorter// make use of excess larger molecules// products more valuable than reactants
18 of 24
Describe hydrocarbons as fuels
non-renewable // over reliance is causing energy crisis// need to develop alternatives // increased CO2 emissions// global warming// climate change // political problems
19 of 24
What are the conditions of catalytic cracking?
low Pa// temp 450oC // zeolite catalyst
20 of 24
Why are high temperatures required in cracking?
strong covalent bonds need to be split
21 of 24
What does catalytic cracking do and why?
turns straight chain alkanes into branched cycloalkanes and aromatic H.carbons // burn cleanly and have higher octane numbers
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What do good fuels have high octane numbers?
lower octane fuels ignite more easily which can damage engines
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How are straight chain hydrocarbons processed into branched/cyclic hydrocarbons?
by isomerism and reformation // isomerism - heat with catalyst and stuck on inert AlO // reformation - heat with palladium alloy catalyst and inert AlO
24 of 24
Other cards in this set
Card 2
Front
How is crude oil separated?
Back
fractional distillation in a fractioning column // oil is heated to 350oC // heavier fractions with higher MP condense first and come off lower in the column // small come off at top
Card 3
Front
What are the non-vaporisable hydrocarbons called?
Back
Card 4
Front
Why do larger hydrocarbons have higher melting points?
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