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A Level Organic Chemistry > Section 2 - Alkanes and Halogenoalkanes > Flashcards

Section 2 - Alkanes and Halogenoalkanes Flashcards

1
Q

What are alkanes?

A

Saturated hydrocarbons

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2
Q

Give the general formula for alkanes:

A

CnH2n+2

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3
Q

What is the general formula for cycloalkanes?

A

CnH2n

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4
Q

What is crude oil/petroleum made up of?

A

A mixture of hydrocarbons - mostly alkanes.

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5
Q

How do you separate crude oil?

A

Through fractional distillation

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6
Q

Describe the process of fractional distillation:

A
  • Crude oil vaporised at 350oc
  • Oil goes into a fractioning column which is hot at the bottom and cool at the top
  • The various alkanes have diff bpts and condense off at different levels
  • The alkanes with the lowest bpts don’t condense and leave the top of the column as gases
  • The alkanes with the highest bpts don’t vaporise and form a gooey residue at the bottom
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7
Q

For each fraction, give the number of carbons and uses:

Gases

A

1-4 carbons

liquified petroleum gas, camping gas

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8
Q

For each fraction, give the number of carbons and uses:

Petrol - 400c

A

5-12 carbons

petrol

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9
Q

For each fraction, give the number of carbons and uses:

Naphtha - 110oc

A

7-14 carbons

processed to make petrochemicals

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10
Q

For each fraction, give the number of carbons and uses:

Kerosene (paraffin) - 180oc

A

11-15 carbons

jet fuel, petrochemicals, central heating fuel

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11
Q

For each fraction, give the number of carbons and uses:

Gas oil (diesel) - 250oc

A

15-19 carbons

diesel fuel, central heating fuel

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12
Q

For each fraction, give the number of carbons and uses:

Mineral Oil - 340oc

A

20-30 carbons

lubricating oil

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13
Q

For each fraction, give the number of carbons and uses:

Residue - Fuel Oil

A

30-40 carbons

ships, power stations

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14
Q

For each fraction, give the number of carbons and uses:

Residue - Wax, grease

A

40-50 carbons

candles, lubrication

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15
Q

For each fraction, give the number of carbons and uses:

Residue - Bitumen

A

50+ carbons

roofing, road surfacing

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16
Q

What is cracking?

A

Breaking long-chain alkanes into smaller hydrocarbons (including alkenes) by breaking the C-C bonds.

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17
Q

Give the features of thermal cracking:

A
  • takes place at high temp (up to 1000oc)
  • takes place at high pressure (up to 70 atm)
  • produces a lot of alkenes
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18
Q

Give the features of catalytic cracking:

A
  • uses a zeolite catalyst
  • uses a high temp (around 450oc)
  • slight pressure (1-2 atm)
  • produces a lot of aromatic hydrocarbons and motor fuels
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19
Q

What is an advantage of thermal cracking?

A

Alkenes are used to make lots of valuable products like polymers (plastics).

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20
Q

What is an advantage of catalytic cracking?

A

Using a catalyst cuts costs because it lowers the temperature and pressure required

It also speeds up the reaction saving time and money

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21
Q

What is a combustion reaction?

A

Burning hydrocarbons with plenty of oxygen to produce carbon dioxide and water.

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22
Q

What is complete combustion?

A

When enough oxygen is available that only carbon dioxide and water are produced

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23
Q

What is incomplete combustion?

A

When not enough oxygen is available to react with the fuel so harmful by-products are produced

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24
Q

Give an advantage and disadvantage of burning fossil fuels:

A

Produces a lot of energy BUT produces lots of pollutants

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25
Why is it bad when carbon monoxide is produced during incomplete combustion?
- it is poisonous - it binds to the same sites on haemoglobin molecules in red blood cells as oxygen molecules so oxygen can't be carried round the body
26
What is a solution to the production of carbon monoxide?
Catalytic converters can remove CO from exhaust gases in cars
27
Why is it bad when carbon particles (soot) are produced during incomplete combustion?
- causes breathing problems - can build up in engines preventing them from working
28
Why is carbon dioxide bad for the environment?
- it is a greenhouse gas - greenhouse gases absorb infrared energy and emit some of it back to Earth, keeping it warm - this process is called global warming
29
What are unburnt hydrocarbons?
Fuel molecules that aren't burn in engines.
30
How are oxides of nitrogen formed?
When the high pressure and temperature in the engine causes nitrogen and oxygen from the air to react
31
What is formed when unburnt hydrocarbons and nitrigen oxides react in the presence of sunlight?
Ground level ozone - O3
32
What is the problem with ground level ozone?
- major component of smog - irritates people's eyes - aggravates respiratory systems - causes lung damage
33
What can prevent the production of nitrogen oxides and unburnt hydrocarbons?
Catalytic converters
34
Why is sulfur dioxide bad for the environment?
Reacts with water to form acid rain
35
How is sulfur dioxide produced?
Some fossil fuels contain sulfur which form SO2 when burnt
36
What is bad about acid rain?
- destroys trees and vegetation - corrodes buildings and statues - kills fish in lakes
37
How can sulfur dioxide be removed from power station flue gases?
- powered calcium carbonate or calcium oxide is mixed with water to make an alkaline slurry - when the flue gases mix with the slurry, sulfur dioxide reacts with the calcium compounds to form a harmless salt - calcium sulfate
38
What is a free radical?
A particle with an unpaired electron.
39
How do free radicals form?
When a covalent bond splits equally, giving one electron to each atom.
40
What is a photochemical reaction?
A reaction that it started by ultraviolet light.
41
What are chlorofluorocarbons?
Halogenoalkane molecules where all of the hydrogen atoms have been replaced by chlorine and fluorine atoms.
42
What does ozone do in the upper atmosphere?
Prevents a lot of UV radiation from reaching earth.
43
Why is UV radiation bad?
It can cause sunburn or even skin cancer.
44
How do CFCS damage the ozone layer?
They are broken down into chlorine radicals. These attack the ozone and break it down into O2 which creates holes in the ozone layer.
45
CFCs are unreactive, non-flammable and non-toxic, what were they used for?
- coolant gases in fridges - solvents - propellants in aerosols
46
What are some safer alternatives to CFCs?
hydroflurorocarbons and hydrocarbons.
47
What are halogenoalkanes?
Alkanes with halogen atoms.
48
Is the carbon halogen bond polar or impolar?
Polar
49
Why are carbons in halogenoalkanes prone to attack from nucleophiles?
They have a delta-positive charge.
50
What is a nucleophile?
A lone pair donor.
51
What is a nucelophilic substitution reaction?
When a nucleophile reacts with a polar molecule by replacing its functional group.
52
What is formed when halogenoalkanes react with hydroxides?
Alcohols
53
What is formed when halogenoalkanes react with cyanide?
Nitriles
54
What is formed when halogenoalkanes react with ammonia?
Amines
55
What are the conditions for the nucleophilic substitution reaction of halogenoalkanes with hydroxides?
- warm - aqueous NaOH or KOH
56
What are the conditions for the nucleophilic substitution reaction of halogenoalkanes with cyanide?
- warm - ethanolic KCN - reflux
57
What are the conditions for the nucleophilic substitution reaction of halogenoalkanes with ammonia?
- warm - ethanolic , excess ammonia
58
What determines the reactivity of halogenoalkanes?
The carbon-halogen bond strength.
59
Does the order of bond strength increase or decrease? C-F C-Cl C-Br C-I
Decreases
60
What is formed when halogenoalkanes undergo elimination?
Alkenes
61
What are the conditions for the elimination reaction of halogenoalkanes with hydroxide ions?
- warm - ethanolic hydroxide ions - reflux
62
What is formed when halogenoalkanes are reacted with hydroxide ions in aqueous conditions?
Alcohol
63
What is formed when halogenoalkanes are reacted with hydroxide ions in anhydrous conditions?
Alkenes
64
What does OH act as in a nucleophilic substitution reaction?
Nucleophile
65
What does OH act as in an elimination reaction?
Base

A Level Organic Chemistry (9 decks)

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