2.5 Hydrocarbons Flashcards
what is a fossil fuel
a fuel which has derived from organisms that lived long ago
state 2 advantages of fossil fuels
- available in a variety of forms
- available at all times (solar+wind have limited availability)
4 disadvantages of fossil fuels
- non renewable + finite resource
- release greenhouse gases
- cause acid rain
- carbon monoxide is formed
what is complete combustion
combustion which occurs with excess oxygen
what is incomplete combustion
combustion which occurs with insufficient oxygen
what are the 2 reactions of alkanes
1: combustion
2: halogenation
what are the products of complete combustion
carbon dioxide + water
what are the products of incomplete combustion
carbon monoxide + water
how is carbon monoxide toxic
it attaches to haemoglobin and prevents it from carrying oxygen round the body
what are the 3 stages of halogenation
- initiation
- propagation
- termination
what is halogenation
the reaction between an organic compound and any halogen
explain stage 1 (initiation) of halogenation
- UV light breaks the bond between halogens homolytically.
- homolytic bond fission occurs when each of bonded atoms receive one of the bond electrons, forming radicals
what are radicals
species with an unpaired electron
what is homolytic bond fission
when a bond is broken and each of the bonded atoms receives one of the bonded electrons
explain stage 2 (propagation) of halogenation
radicals are very reactive, taking part in propagation reactions
a chain reaction occurs
explain stage 3 (termination) of halogenation
the reaction stops due to 2 radicals meeting.
write an equation for the reaction of ethane with bromine
C₂H₆ + Br₂ –> C₂H₅Br + HBr
how are alkenes formed
when petroleum is cracked
what is heterolytic bond fission
when a bond is broken and one of the bonded atoms receives both of the bonded electrons
what is the use of electrophilic addition and bromine
a test for alkenes.
bromine is brown. alkene presence shows a discolouration.
what is the use of electrophilic addition and hydrogen
hydrogenation.
(catalysed by platinum/palladium/nickel)
hardened liquid vegetable oil = solid fats
what is polymerisation
joining of large numbers of monomers = giant polymer molecule
name 3 important polymers
- poly(propene)
- poly(chloroethene)
- poly(phenylethene)
what is the purpose of polypropene
used in kitchen equipment + food containers (rigid)
