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Chemistry > 3.3.2-Alkanes > Flashcards

3.3.2-Alkanes Flashcards

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1
Q

What is petroleum

A

It is a complex mixture of hydrocarbons

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2
Q

2 features of petroleum

A

Mainly alkanes which are hydrocarbons

When first extracted is almost useless

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3
Q

How is petroleum separated

A

Fractional distillation

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4
Q

3 key points of fractional distillation

A

Relies on hydrocarbon chains length being different so bp are different

Long chains have higher boiling point than short Chains

Long chains move toward bottom and short chains to top

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5
Q

Uses of fractions

A

Fuels
Petrochemicals
Feedstock for cracking

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6
Q

Why do we do cracking

A

There are a shortage of some chain length and a surplus of others as well alkenes are in high demand to make polymer which can only be found through cracking

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7
Q

What does a high mr make after cracking

A

Small mr + alkenes + hydrogen

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8
Q

What are the conditions of thermal cracking

A

High temperature 400-600

High pressure (7,000Kpa)

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9
Q

What are the products of thermal cracking

A

Alkenes

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10
Q

What are the uses of the products from thermal cracking

A

Chemical feedstock and conversion to polymers

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11
Q

Thermal cracking
Conditions
Products
Uses

A

High temperature
High pressure

Alkenes

Chemical feedstock and conversion to polymers

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12
Q

Catalytic cracking

Conditions

A

High temp -450
Slight pressure
Zeolite catalyst

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13
Q

Products of catalytic cracking

A

Branched alkanes, cyclohexane, aromatic hydrocarbons

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14
Q

Uses of products of catalytic cracking

A

Motor fuels

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15
Q

Methane use when burned

A

Natural gas, cooking , heating , electric

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16
Q

Combustion of propane uses

A

Camping fuel , domestic fuel and industrial fuel

17
Q

Combustion of butane uses

A

Camping fuel and lighters

18
Q

Uses of octane combustion

A

In petrol

19
Q

What is complete combustion conditions and products

A

Excess of oxygen

Products CO2 and H20

20
Q

What are conditions and products of incomplete combustion

A

Limited supply of oxygen
Products CO,C and H2O

CO is poisonous

21
Q

What are the the pollutant produced by car engines

A

CO

NOx

Unburnt hydrocarbons

22
Q

How is Co formed and the problem

A

Incomplete combustion

Poisonous gas

23
Q

How are NOx formed and the problem

A

N2 and O2 react at high temperatures in engine

Combine with water to make acid rain and chemical smog

24
Q

How NOx forms acid rain equation

A

4NO+O2+H2O - HNO3

25
Q

How does NOx form chemical smog equation

A

4NO+O2+2H2O - 4HNO3

26
Q

How are unburnt hydrocarbons formed and the problem

A

Engine not hot enough

Makes photochemical smog irritating to lungs

27
Q

What is a catalytic converter

A

Catalytic converters are honeycomb of ceramic material coated with catalytic metals in thin layers

28
Q

Examples of catalysts

A

Platinum, palladium , rhodium

29
Q

How is NOx and CO changed to harmless gas in catalytic converter

A

NOx
C

Adsorb onto catalyst and react to form N2 and CO2

2NO+2CO- N2 +2CO2
NO2 +4CO - N2 + 4CO2

30
Q

How do unburnt hydrocarbons change to unharmful compounds

A

React with NO to produce CO2 and H20 and N2

C8H18+25NO-8CO2+9H2O+12.5H2O

31
Q

What happens when fossil fuels contain sulphur

A

S+O2 burns to make SO2

This goes into the air

32
Q

What is the problem with SO2

A

SO2 in the air with water forms H2SO3 which is acid rain

33
Q

How do you remove SO2

A

FGD(flue gas desulphisers)

Passed through CaO
SO2+ CaO–CaSO3
Oxidised
CaSO3+1/2O2 – CaSO4

34
Q

How can CaSO4 be used after it is formed

A

Can be used as gypsum in plaster

35
Q

What are the greenhouse gases

A

Carbon dioxide
Methane
Water

36
Q

What do the greenhouse gases do

A

Absorb some of infa-red energy
Molecules then emit energy in all directions
Some returns to surface to keep warm

37
Q

Impact of global warming

A

Ice in polar regions are melting and retreating

Sea levels rising

Chemistry (29 decks)

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