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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
Q

Why is it bad when carbon monoxide is produced during incomplete combustion?

A
  • 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
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26
Q

What is a solution to the production of carbon monoxide?

A

Catalytic converters can remove CO from exhaust gases in cars

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27
Q

Why is it bad when carbon particles (soot) are produced during incomplete combustion?

A
  • causes breathing problems
  • can build up in engines preventing them from working
28
Q

Why is carbon dioxide bad for the environment?

A
  • 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
Q

What are unburnt hydrocarbons?

A

Fuel molecules that aren’t burn in engines.

30
Q

How are oxides of nitrogen formed?

A

When the high pressure and temperature in the engine causes nitrogen and oxygen from the air to react

31
Q

What is formed when unburnt hydrocarbons and nitrigen oxides react in the presence of sunlight?

A

Ground level ozone - O3

32
Q

What is the problem with ground level ozone?

A
  • major component of smog
  • irritates people’s eyes
  • aggravates respiratory systems
  • causes lung damage
33
Q

What can prevent the production of nitrogen oxides and unburnt hydrocarbons?

A

Catalytic converters

34
Q

Why is sulfur dioxide bad for the environment?

A

Reacts with water to form acid rain

35
Q

How is sulfur dioxide produced?

A

Some fossil fuels contain sulfur which form SO2 when burnt

36
Q

What is bad about acid rain?

A
  • destroys trees and vegetation
  • corrodes buildings and statues
  • kills fish in lakes
37
Q

How can sulfur dioxide be removed from power station flue gases?

A
  • 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
Q

What is a free radical?

A

A particle with an unpaired electron.

39
Q

How do free radicals form?

A

When a covalent bond splits equally, giving one electron to each atom.

40
Q

What is a photochemical reaction?

A

A reaction that it started by ultraviolet light.

41
Q

What are chlorofluorocarbons?

A

Halogenoalkane molecules where all of the hydrogen atoms have been replaced by chlorine and fluorine atoms.

42
Q

What does ozone do in the upper atmosphere?

A

Prevents a lot of UV radiation from reaching earth.

43
Q

Why is UV radiation bad?

A

It can cause sunburn or even skin cancer.

44
Q

How do CFCS damage the ozone layer?

A

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
Q

CFCs are unreactive, non-flammable and non-toxic, what were they used for?

A
  • coolant gases in fridges
  • solvents
  • propellants in aerosols
46
Q

What are some safer alternatives to CFCs?

A

hydroflurorocarbons and hydrocarbons.

47
Q

What are halogenoalkanes?

A

Alkanes with halogen atoms.

48
Q

Is the carbon halogen bond polar or impolar?

49
Q

Why are carbons in halogenoalkanes prone to attack from nucleophiles?

A

They have a delta-positive charge.

50
Q

What is a nucleophile?

A

A lone pair donor.

51
Q

What is a nucelophilic substitution reaction?

A

When a nucleophile reacts with a polar molecule by replacing its functional group.

52
Q

What is formed when halogenoalkanes react with hydroxides?

53
Q

What is formed when halogenoalkanes react with cyanide?

54
Q

What is formed when halogenoalkanes react with ammonia?

55
Q

What are the conditions for the nucleophilic substitution reaction of halogenoalkanes with hydroxides?

A
  • warm
  • aqueous NaOH or KOH
56
Q

What are the conditions for the nucleophilic substitution reaction of halogenoalkanes with cyanide?

A
  • warm
  • ethanolic KCN
  • reflux
57
Q

What are the conditions for the nucleophilic substitution reaction of halogenoalkanes with ammonia?

A
  • warm
  • ethanolic , excess ammonia
58
Q

What determines the reactivity of halogenoalkanes?

A

The carbon-halogen bond strength.

59
Q

Does the order of bond strength increase or decrease?

C-F

C-Cl

C-Br

C-I

60
Q

What is formed when halogenoalkanes undergo elimination?

61
Q

What are the conditions for the elimination reaction of halogenoalkanes with hydroxide ions?

A
  • warm
  • ethanolic hydroxide ions
  • reflux
62
Q

What is formed when halogenoalkanes are reacted with hydroxide ions in aqueous conditions?

63
Q

What is formed when halogenoalkanes are reacted with hydroxide ions in anhydrous conditions?

64
Q

What does OH act as in a nucleophilic substitution reaction?

A

Nucleophile

65
Q

What does OH act as in an elimination reaction?

A Level Organic Chemistry (9 decks)

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