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Chemistry > Alkanes > Flashcards

Alkanes Flashcards

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1
Q

What are crude oils? (3)

A

A finite source found in rocks

The remains of ancient biomass consisting of mainly plankton that was buried in mud

A mixture of a very large number of compounds (mostly hydrocarbons)

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2
Q

What are alkanes?

A

They are saturated hydrocarbons meaning they contain carbon and hydrogen atoms only as well as only containing single bonds

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3
Q

Describe the fractional distillation process (5)

A

Crude oil is heated to vaporise it

The vapour is passed into the column

There is a temperature gradient so the column is hot at the top and cooler at the bottom

Fractions are separated due to their different boiling points so they condense at different levels and are removed

Fractions with low boiling points are collected at the top whereas hotter ones are collected at the bottom

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4
Q

Name the order of fractions from the top of the column to the bottom (8)

A

Refinery gas

Gasoline
Naptha
Kerosene
Diesel oil
Lubricating oil
Fuel oil
Bitumen

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5
Q

Define cracking

A

A process where long chain hydrocarbons are broken into smaller chain hydrocarbons

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6
Q

Why does cracking require high temperatures

A

A lot of energy is required to break the strong C-C bonds

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7
Q

What are 2 conditions for thermal cracking
What are the products (2)

A

High temperatures of around 1200K
High pressures of around 7000kPa

A large proportion of alkenes and a lower proportion of branched alkanes

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8
Q

Define thermal cracking

A

A process used to split long chain alkanes into shorter alkanes and alkenes

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9
Q

Define catalytic cracking

A

A process used to split long chain alkanes into shorter alkanes and alkenes

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10
Q

What are 3 conditions for catalytic cracking

What are the products (2)

A

Relatively low temperatures (700K)
Requires only a slight pressure
A zeolite catalyst

A large proportion of branched alkanes and arenes

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11
Q

What is thermal cracking used for and what is the mechanism

A

Polymers

Free radical

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12
Q

What is catalytic cracking used for and what is the mechanism

A

Motor fuels

Carbocation

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13
Q

What type of process is the combustion of alkanes

What does this make them good for and why

A

Highly exothermic process

Good fuels because they release relatively large amounts of energy per gram of fuel

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14
Q

How do you write balanced combustion equations

A

Balance in alphabetical order

Make sure the moles of the fuel remains 1

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15
Q

What products can be formed in incomplete combustion

A

Carbon monoxide or carbon and water

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16
Q

How does the wording of the question tell you which pollutant is formed in incomplete combustion

A

CO = gaseous pollutant

C = solid pollutant

17
Q

Which alkanes are used as fuels in internal combustion engines

A

Those with the chain lengths of 5 to 10

18
Q

How is nitrogen monoxide formed in IC engines and why

What is the equation to show this

A

Nitrogen and Oxygen react to form NO

Because the temperatures in the engine can reach over 2000 degrees C

N2 + 02 = 2NO

19
Q

What is the equation for when nitrogen monoxide reacts more to form nitrogen dioxide

A

2NO + O2 = 2NOz

20
Q

How does nitrogen dioxide form acid rain

What is the equation for it

A

It reacts with rain water and more oxygen to form nitric acid which contributes to acid rain

4NOz + 2HzO + Oz = 4HNO3

21
Q

What is a catalytic converter used for

A

It is used to transform pollutant gases in a cars exhaust engine into harmless gases

22
Q

What are 3 gases that go into catalytic converters from the engine

A

Carbon monoxide
Nitrogen oxides
Unburnt hydrocarbons

23
Q

What is the catalyst in the catalytic converters

A

Rhodium

24
Q

What are 3 exhaust gases from catalytic converters

A

Carbon dioxide

Nitrogen

Carbon dioxide + water

25
Q

How is Carbon monoxide removed in car engines? (Symbol + written equations)

A

Carbon monoxide + oxygen = carbon dioxide

2CO + Oz = 2COz

26
Q

How are carbon monoxide and nitrogen monoxide removed from car engines together? (Written + symbol equation)

A

Carbon monoxide + nitrogen monoxide = carbon dioxide + nitrogen

2CO + 2NO = 2COz + Nz

27
Q

How is nitrogen monoxide removed from car engines (written + symbol)

A

Nitrogen monoxide = nitrogen + oxygen
2NO = Nz + Oz

28
Q

How are unburnt hydrocarbons removed from car engines

A

By reacting them with oxygen to form carbon dioxide and water (combustion)

29
Q

How are unburnt hydrocarbons and nitrogen monoxide removed together in car engines (2)

A

Octane + nitrogen monoxide = carbon dioxide + nitrogen + water

Reacting then together to form CO2 and N2 and HzO

30
Q

Write an equation for the reaction of sulfur with oxygen

A

Forms Sulfur dioxide

S + O2 = SOz

31
Q

Write the equation to show the further oxidation of sulfur dioxide

A

2SOz + O2 = 2SO3

Forms sulfur trioxide

32
Q

What does sulfur dioxide and sulfur trioxide form when dissolved in water

A

Sulfur dioxide forms sulfurous acid which is HzSO3

Sulfur trioxide forms sulfuric acid which is H2SO4

They both form acidic solutions

33
Q

How is acid rain caused

A

When acidic non metal oxides such as sulfur oxides and nitrogen oxides dissolve in rain water

34
Q

What are flue gases

A

The gas produced at power plants exiting to the atmosphere by a flue which is a pipe or an opening in a chimney

35
Q

How are acidic sulfur oxides removed from flue gases

What type of reaction is it and what is it called

A

By reacting them with a base such as calcium oxide

Neutralisation
Flue gas desulfurisation

36
Q

What is the equation when calcium oxide is used to remove sulfur dioxide from flue gases

A

SO2 + CaO = CaSO3

Chemistry (23 decks)

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