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AQA A Level Chemistry > Organic Chapter 2: Alkanes & Halogenoalkanes > Flashcards

Organic Chapter 2: Alkanes & Halogenoalkanes Flashcards

1
Q

What is the General Formula for an alkane?

A

CnH2n+2

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2
Q

What is an alkane?

A

A saturated hydrocarbon

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3
Q

What is the general formula for a Cycloalkane?

A

CnH2n

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4
Q

What is Crude Oil mostly made up of?

A

Alkanes

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5
Q

Why do we separate Crude Oil?

A

It’s not very useful in raw form

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6
Q

How do we separate Crude Oil?

A

Fractional Distillation

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7
Q

How does Fractional Distillation work?

A

Crude Oil is vaporised at around 350 degrees C
Vaporised Crude Oil goes to the top of the fractioning column
Crude Oil vapour gets cooler as it goes up the column
Each different chemical condenses at a different temperature - liquids get filtered off
Hydrocarbons with lowest & highest bp are taken at the top & bottom of the column respectively

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8
Q

How can you separate long chain hydrocarbons?

A

Cracking

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9
Q

What are the two types of Cracking?

A

Thermal Cracking
Catalytic Cracking

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10
Q

What are the conditions for Thermal Cracking? What does it mainly produce?

A

High pressure & High temp (up to 70atm & 1000 degrees C)
Produces a lot of alkenes

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11
Q

What are the conditions for Catalytic cracking? What does it mainly produce?

A

Takes place in the prescence of a Zeolite Catalyst at a slight pressure & high temperature (450 degrees)
Mostly produces aromatic compounds
Catalytic cracking is cheaper and faster.

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12
Q

What are alkanes useful for?

A

Fuels

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13
Q

What causes incomplete combustion?

A

Lack of oxygen

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14
Q

What is the equation for incomplete combustion of methane?

A

2CH4 + 3O2 -> 2CO + 4H2O

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15
Q

Why does burning fossil fuels contribute to global warming?

A

It produces carbon dioxide - this is a greenhouse gas.

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16
Q

What do Catalytic converters do on cars?

A

Remove unburnt hydrocarbons & oxides of nitrogen from the exhaust

17
Q

What causes acid rain?

A

Sulfur Dioxide

18
Q

What is a Free Radical?

A

A particle with an unpaired electron

19
Q

What causes free radicals to form?

A

When a covalent bond splits equally - both atoms get 1 of the shared electrons

20
Q

What is special about free radicals?

A

They’re very reactive due to the single unpaired electron

21
Q

How do you indicate a free radical?

A

Dot next to the chemical

e.g Cl.

22
Q

What is an initiation step?

A

A step in a reaction where free radicals are produced

23
Q

What is a propagation step?

A

Free radicals are both used up & created

24
Q

What is a termination step?

A

Free radicals are completely used up

25
Q

Why are CFCs now banned?

A

Because they produced chlorine free radicals and caused ozone layer damage

26
Q

What is the equation for chlorine free radicals breaking down the ozone layer?

A

Overall: 2O3 -> 3O2

Cl2 -> 2Cl.
Cl. + O3 -> O2 + ClO.
ClO. + O3 -> 2O2 + Cl.
2Cl. -> Cl2

27
Q

Under what conditions do free radicals form?

A

Prescence of UV light

28
Q

What is a Halogenoalkane?

A

An alkane with a halogen atom on it

29
Q

What is special about the carbon-halogen bond in a halogenoalkane?

A

It’s polar

30
Q

What are some nucleophiles that can react with halogenoalkanes?

A

OH-
CN-
NH3

31
Q

What reaction do Halogenalkanes undergo to become alcohols?

A

Nucleophilic substitution
warm Aqueous sodium or potassium hydroxide

32
Q

What reaction do Halogenoalkanes undergo to become Nitriles?

A

Nucleophilic substitution
Warmed ethanolic potassium cyanide
Heat under Reflux

33
Q

What reaction do Halogenoalkanes undergo to become Amines?

A

Nucleophilic substitution
Excess Ethanolic Ammonia

34
Q

Which Halogenoalkanes react the fastest and which the slowest?

A

Iodoalkanes are the fastest
Flouroalkanes are the slowest

35
Q

What reaction do halogenoalkanes undergo to become Alkenes?

A

Elimination
Ethanolic hydroxide ions
Heat under reflux

AQA A Level Chemistry (25 decks)

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