Alkanes Flashcards

1
Q

What are structural isomers

A
  • same molecular formula but different arrangement of atoms
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2
Q

I hat does fractional distillation use to separate fractions

A

Boiling point

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3
Q

Trend in boiling point of alkanes

A

As carbon chain increase = boiling point increase

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4
Q

What is cracking

A
  • breaks down large alkanes into smaller alkanes + alkenes
  • happens at high temps + uses a catalyst = Zeolite
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5
Q

What is reforming

A
  • converts un-branched hydrocarbons into branched or cyclic hydrocarbons
  • due to them burning better in vehicle engines
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6
Q

What is a bi product of reforming

A

Hydrogen gas

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7
Q

What 2 dangerous gasses occur in fuel combustion in a vehicle engine

A
  • Nitrogen oxides + sulphur dioxide
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8
Q

What impurities do hydrocarbon fuels usually contain

A

Sulphur
Oxidised to SO2 In combustion of fuel
S + O2 = S02

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9
Q

How are nitrogen oxides produced

A

Nitrogen in air reacts with oxygen at high temps of combustion engine
- N2 + O2 = 2NO

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10
Q

Why are oxides of sulphur + nitrogen dangerous

A

Accidic
Produce acid rain = kills plant life

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11
Q

Give 2 examples of alternative fuels

A

Biodiesel + Bioalcahol

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12
Q

Advantage + disadvantage of biodiesel

A

+ Made from vegetable oils ( Soya or Sunflower)

  • NaOH needed to manufacture = this must be manufactured
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13
Q

Advantage + disadvantage of Bioalcohol

A

+ produced by fermentation of plant sugars = renewable

  • CO2 produced in fermentation process
    Fermentation is slow
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14
Q

How do alkanes react with halogens or hydrogen halides

A

Free radical substitution

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15
Q

Give the initiation, propagation + termination steps of :
CH4 + Cl2

A

Initiation - Cl2 = 2Cl•
Propagation - CH4 + Cl• = CH3• + HCl

                    CH3• + Cl2 = CH3Cl + Cl• Termination - any 2 radicals together  Eg : CH3• + CH3• = C2H6
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16
Q

What breaks the bond between the Cl2 in free radical substitution + what kind of bond breaking is this

A

UV light
Homolytic fission producing 2 Radicals

17
Q

What is a radical

A

Species with an unpaired electron