Topic 12: Alkanes Flashcards
Alkanes general formula
CnH2n+2
Hydrocarbons
Molecules that only contain Carbon and Hydrogen
Crude Oil
Mixture of different hydrocarbons
Alkanes bp
Bigger chain higher boiling point - more electrons, stronger v.d.w
Fractional Distillation
- Crude oil heated + enters column as vapour
- Vapour rises up the column cooling as it goes
- Varying lengths of alkanes have varying boiling points
- Alkanes condense at their bp allowing them to be separated and pumped away seperately
Alkene test
Bromine water
Orange - colourless as unsaturated
Catylitic cracking conditions… producing
Lower temp 450*C with zeolite catalyst (aluminosilicate) low pressure
- forms aromatic compounds + fuels
Thermal cracking condtions
High temp 450-750*C and high pressure 7000kPa
Complete combustion def
Burning a fuel in fully excess oxygen producing co2 and h2o
Complete combustion equation
FUEL + O2 —> CO2 + H2O
Incomplete combustion
Burning a fuel in not enough oxygen producing CO/C and H2O
Incomplete combustion eq’ns
FUEL + O2 —> CO(g) + H2O
FUEL + O2 —> C(s) + H2O
Carbon monoxide and carbon (soot)
Fuel containing sulphur affects when combust
Oxidised to produce S02(g) which forms acid rain in the atmosphere with water vapour and oxygen making H2SO4
Flue-gas desulphurisation
Removing the SO2 using CaO (base) to produce CaSO3 which is further oxidised to form CaSO4 (gypsum) used for plastering
Nitrogen Oxides
NOx - NO, NO2
In the engine high heat and pressure allow nitrogen to react with O2 in the air producing these
NOx comes from and turns to…
N2 + O2 —> 2NO (toxic, acid rain, respiritory problems)
2NO + O2 —> 2NO2
Catalytic converter
Honeycomb shape made of Pt and Rh large S.A. so more sites for catalysing, aren’t used up quickly as catalyst
Catalyse these reactions
2NO —> N2 + O2
2NO + 2CO —> N2 + CO2
Unburnt hydrocarbons
Particulates - respiratory problems
Greenhouse Affect
Greenhouse gases causes more IR to be absorbed leads to the enhanced greenhouse effect - global warming/ climate change
