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A Level Chemistry Y1 > Alkanes > Flashcards

Alkanes Flashcards

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1
Q

general formula for alkanes?

A

Cn H2n+2

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2
Q

what type of molecule are all alkanes

A

simple molecular

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3
Q

describe + explain trend in alkane boiling point

A

as the straight chain gets longer, the boiling point increases

  • longer chain = larger surface area contact
  • large SA contact = stronger VdW forces = high boiling point
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4
Q

what is crude oil

A

a mixture of different length hydrocarbons

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5
Q

what method is used to separate different alkanes in crude oil

A

fractional distillation

  • crude oil is vaporised and put into a tower which is hotter a the bottom and colder at the top
  • as vapour rises it cools and will condense at different heights as they have different boiling points
  • larger molecule = lower down the column it condenses
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6
Q

what happens to the hydrocarbons as the carbon chain gets longer

A
  • become more viscous (thick)
  • harder to ignite
  • less volatile
  • have higher boiling points
  • have stronger VdW forces between molecules
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7
Q

what method do you use to split longer hydrocarbons into shorter ones

A

thermal cracking and catalytic cracking

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8
Q

what are the conditions of thermal cracking

A
  • high temperature
  • high pressure
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9
Q

what does thermal cracking produce

A
  • produces a high percentage of alkenes and straight-chain alkanes
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10
Q

what are the conditions of catalytic cracking

A
  • high temperature
  • slight/moderate pressure
  • zeolite catalyst
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11
Q

what does catalytic cracking produce

A
  • produces motor fuels ( short chain alkanes), aromatic hydrocarbons and cycloalkanes
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12
Q

what products form from the complete combustion of alkanes?

A

carbon dioxide and water

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13
Q

what products form from the incomplete combustion of alkanes?

A

carbon and/or carbon dioxide

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14
Q

why is complete combustion more cost-effective than incomplete combustion

A
  • complete combustion is more exothermic
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15
Q

name 5 pollutants from incomplete combustion?

A
  • carbon monoxide
  • carbon particulates
  • unburnt hydrocarbons
  • nitrogen di/oxide(s)
  • sulfur dioxide
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16
Q

how is carbon monoxide made , what problems does it cause and how is the problem solved

A
  • formed by incomplete combustion of carbon containing fuels
  • toxic gas
  • solved by catalytic converters (in cars)
17
Q

how are carbon particulates made , what problems do they cause and how is the problem solved

A
  • formed by incomplete combustion of carbon containing fuels
  • can cause respiratory problems
  • solved by ensuring there’s a good supply of oxygen when burning fuels
18
Q

how are unburnt hydrocarbons made , what problems do they cause and how is the problem solved

A
  • formed by hydrocarbons not burning
  • causes photochemical smug
  • solved by catalytic converters (in cars)
19
Q

how is nitrogen di/oxide(s) made , what problems does it cause and how is the problem solved

A
  • combustion of nitrogen and oxygen in the air at high temperatures
  • causes acid rain (when reacted with water)
  • solved by catalytic converters (in cars)
20
Q

how is sulfur dioxide made , what problems does it cause and how is the problem solved

A
  • formed by combustion of sulfur containing compounds in fuels
  • causes acid rain (when reacted with water)
  • solved by flue gas desulfurization
21
Q

how does flue gas desulfurization work

A

Removing sulfur compounds by reacting them with limestone (CaCO3) or lime (CaO)

22
Q

what are the equations for flue gas desulfurization

A

CaCO 3(s) + SO 2(g) → CaSO 3(s) + CO

CaO + SO2→ CaSO3

23
Q

what is a catalytic converter

A

a catalytic converter changes harmful compounds from an engine’s emissions into safe gases, like steam.

24
Q

features of a catalytic converter + link to function

A
  • honey comb structure = increases the surface area
  • made of a ceramic material = withstands high temperatures inside the combustion engine
  • honeycomb has thin coat of platinum, palladium, rhodium = reduces cost (thin)
25
Q

nitrogen combustion equation

A

N₂ + O₂ → NO/NO₂/NO₃/2NO

A Level Chemistry Y1 (16 decks)

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