Alkanes Flashcards
What are structural isomers
- same molecular formula but different arrangement of atoms
I hat does fractional distillation use to separate fractions
Boiling point
Trend in boiling point of alkanes
As carbon chain increase = boiling point increase
What is cracking
- breaks down large alkanes into smaller alkanes + alkenes
- happens at high temps + uses a catalyst = Zeolite
What is reforming
- converts un-branched hydrocarbons into branched or cyclic hydrocarbons
- due to them burning better in vehicle engines
What is a bi product of reforming
Hydrogen gas
What 2 dangerous gasses occur in fuel combustion in a vehicle engine
- Nitrogen oxides + sulphur dioxide
What impurities do hydrocarbon fuels usually contain
Sulphur
Oxidised to SO2 In combustion of fuel
S + O2 = S02
How are nitrogen oxides produced
Nitrogen in air reacts with oxygen at high temps of combustion engine
- N2 + O2 = 2NO
Why are oxides of sulphur + nitrogen dangerous
Accidic
Produce acid rain = kills plant life
Give 2 examples of alternative fuels
Biodiesel + Bioalcahol
Advantage + disadvantage of biodiesel
+ Made from vegetable oils ( Soya or Sunflower)
- NaOH needed to manufacture = this must be manufactured
Advantage + disadvantage of Bioalcohol
+ produced by fermentation of plant sugars = renewable
- CO2 produced in fermentation process
Fermentation is slow
How do alkanes react with halogens or hydrogen halides
Free radical substitution
Give the initiation, propagation + termination steps of :
CH4 + Cl2
Initiation - Cl2 = 2Cl•
Propagation - CH4 + Cl• = CH3• + HCl
CH3• + Cl2 = CH3Cl + Cl• Termination - any 2 radicals together Eg : CH3• + CH3• = C2H6