Alkanes
Uses
Used as fuels
Properties
 Boiling point increases with increasing size of alkane because
intermolecular forces increase as a molecule gets bigger.
 Chemically quite unreactive
 SATURATED – only contain C-C single bonds
Reactions
Complete Combustion
Burnt in excess oxygen to produce CO2 and H2O
eg for methane: CH4 + 2O2 → CO2 + 2H2O
(you need to be able to write and balance for any alkane given)
Incomplete Combustion
Burnt with insufficient oxygen to produce CO and H2O
eg for methane: CH4 + 1½O2 → CO + 2H2O
(you need to be able to write and balance for any alkane given)
This reaction may also produce soot (C)
Carbon monoxide, CO, is extremely toxic. People have died as a result
of poorly serviced boilers (eg blocked vents) burning fuel
incompletely.
Reaction with Cl2 or Br2
Alkanes react with chlorine or bromine only in the presence of ultra
violet light (UV light).
The reaction is a SUBSTITUTION reaction (a hydrogen has been
swapped for a bromine)
CH4 + Br2 → CH3Br + HBr (in UV light)