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ALKANES Flashcards

1
Q

Define saturated

A

No double bond

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2
Q

Define hydrocarbon

A

Molecule containing only C and H

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3
Q

What two factors affect alkane boiling points

A

Carbon chain length, number of branches

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4
Q

Boiling point increases as chain length increases because:

A

•alkanes have induced dipole dipoles between molecules
•strength of bonds increases as size of molecule increases
•the longer the C chain, the bigger the molecule, the more e-

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5
Q

How do more branches affect boiling point?

A

•more branches decrease boiling point
•there is more surface contact between lower branched molecules
•the induced dipole dipole attractions between molecules of lower branched molecules are stronger

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6
Q

How does fractional distillation work?

A

Separates hydrocarbons based on their different boiling points

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7
Q

What is a fraction

A

A group of hydrocarbons with the same boiling point

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8
Q

What is the process of fractional distillation? (6m)

A

•crude oil is vapourised and enters column at the bottom
• the mixture of HC have different boiling points
•their boiling points depend on chain length and branching
•it is hotter at the bottom of the column
•larger molecules condense first at the bottom and collect

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9
Q

What is cracking?

A

Breaks larger fractions into smaller fractions

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10
Q

Why do we use cracking?

A

To produce more useful, shorter chain molecules that are higher in demand

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11
Q

What does thermal cracking use

A

High temperature and pressure

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12
Q

What temperature does thermal cracking use?

A

700-1200K

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13
Q

What pressure does thermal cracking use?

A

7000kPa

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14
Q

What are the products of thermal cracking?

A

One alkane, the rest alkenes

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15
Q

What temperature does catalytic cracking use?

A

720K

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16
Q

What pressure does catalytic cracking use?

A

100kPa

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17
Q

What catalyst does catalytic cracking use?

A

Zeolite

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18
Q

What is produced with catalytic cracking?

A

High percentage of branched alkanes and cycloalkanes

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19
Q

What are cycloalkanes used for?

A

Motor fuels

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20
Q

What is combustion?

A

Reaction with oxygen

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21
Q

What is needed for complete combustion

A

Excess oxygen

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22
Q

What are the products of complete combustion?

A

CO2 and H2O

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23
Q

What is the reaction for complete combustion of methane

A

CH4 + 2O2 -> CO2 + H20

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24
Q

What is methane used for?

A

Domestic heating and cooking

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25
What are products of incomplete combustion?
CO and H20
26
Why is CO harmful
Toxic as it prevents oxygen from binding to haemoglobin in blood cells
27
What are two harmful products of combustion
SO2 and NO2
28
Equation for production of SO2
S(s) + O2 -> SO2
29
Why is sulfur dioxide formed?
Sulfuric impurities appear in crude oil
30
What does sulfur oxide and nitrogen oxide cause
Acid rain
31
Why is acid rain harmful
Causes erosion of buildings and lake contamination
32
What does sulfur dioxide do in rain water
Dissolve
33
Give the equation of the reaction of SO2 with rain water
SO2 + 1/2 O2 + H2O -> H2SO4
34
Why are nitrogen oxides formed after combustion?
Fuels burn in air which is 80% oxygen
35
Give equation for the formation of nitrogen oxide
N2 + O2 -> 2NO
36
Give equation for the formation of nitrogen dioxide
2NO + O2 -> 2NO2
37
What is the equation with nitrogen that causes acid rain
4NO2 + 2H2O + O2 -> 4HNO3
38
Why are unburnt hydrocarbons harmful
Toxic and cause cancer
39
How do unburnt hydrocarbons arise
Escape into air before being used up
40
What are the two ways to reduce pollution
Fluent gas desulphurisation and catalytic converter
41
How does flue gas sulphurisation work
Neutralises acidic SO2 with alkali
42
What does flue gas desulfurisation use
Calcium oxide and calcium carbonate
43
What does the reaction with calcium oxide and SO2 produce
CaSO4.2H2O
44
What is CaSO4.2H2O used for
Builders' plaster
45
What does calcium carbonate and SO2 produce
CaSO4
46
How does a catalytic converter work?
Converts harmful gases into less harmful gases
47
What is the structure of a catalytic converter?
Honeycomb
48
Why does a catalytic converter have a honeycomb structure?
Increased surface area for a faster rate of reaction
49
What metals is a catalytic converter made of
Platinum and rhodium (catalysts)
50
What does NO and CO produce in a catalytic converter?
N2 and CO2
51
What do unburnt hydrocarbons and NO produce in a catalytic converter
CO2 H2O N2
52
Polluting effect of CO2
Greenhouse gas
53
Polluting effect of H2O
Greenhouse gas
54
Polluting effect of CO
Poisonous
55
Polluting effect of solid Carbon
Damages lungs
56
Three characteristics of the homologous series are:
•differ by CH2 •chemically similar •show a trend in physical properties
57
The order of fractions from lowest boiling point to highest
Mineral oil, gas oil (diesel), kerosene (paraffin), naphtha, petrol (gasoline)
58
What does the term carbon-neutral mean?
An activity with no overall carbon emissions
59
What is the use of a short chain alkane?
Fuel
60
What is the use of a long chain alkane
Any of the high BP fractions eg. Fuel oil, kerosene, petrol
61
Use of an alkene
Poly (alkene)
62
How are nitrogen oxides formed in engines (2m)
•N2 reacts with oxygen IN AIR •at high temperatures
63
With which mechanism does chlorination occur?
Free-radical substitution
64
What are the reagents and conditions of chlorination
Cl2 , UV light
65
What are the steps in chlorination/free radical substitution?
•initiation •propagation •termination
66
What is the equation of the initiation step of chlorination
UV light Cl2 ----> 2Cl•
67
What is the propagation step of chlorination of ethane?
Cl• + CH3CH3 --> •CH2CH3 + HCl •CH2CH3 +Cl2 --> CH2ClCH3 + Cl•
68
What is the termination step of chlorination?
Two radicals combine

CHEMISTRY (12 decks)

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