DJA 4). Alkanes Flashcards
what are alkanes
saturated hydrocarbons containing only c-c and c-h single bonds
general formula of alkanes
CnH2n+2
what is crude oil
a mixture of hydrocarbons of different sizes
not very useful and needs to be separated
how to separate crude oil
fractional distillation
how fractional distillation works
heated to vapour
fed up fractionating column
fractionating tower has a temperature gradient: hot at bottom, cool at top
as vapour rises it cools and condense at their boiling points and are separated off. longest chains at bottom, shortest at the top
as the carbon chains get longer, the hydrocarbons…
viscosity, ignition, volatile, boiling point
- become more viscous
- harder to ignite
- less volatile
- have higher boiling points
why crack
to break down long chain, in less demand, alkanes into short chain, more commercially useful,
thermal cracking conditions
700-1,200K
7,000kPa
thermal cracking tend to produce
short chain alkenes (and alkanes)
middle step of thermal cracking
free radicals form
catalytic cracking conditions
720K
low pressure
zeolite (honeycomb structure -large surface area, aluminosilicates)
catalytic cracking tends to produce…
branched alkanes, cycloalkanes, aromatic compounds
3 different products of combustion (complete and both types of incomplete)
CO2 + H2O colourless gas
CO + H2O toxic gas
C + H2O black solid
side products of the internal combustion engine and where they come from
NOx from the air
SO2 from sulfur in coal
unburnt hydrocarbons
equation for N2 into NO
N2 + O2 —-> 2NO
how SO2 turns into acid rain
SO2 + H2O —> H2SO3
H2SO3 + H2O —–> H2SO4
how sulfur is prevented and chemical equation
flue gas desulphurisation, SO2 is removed by reacting the coal with CaO
SO2 + CaO + 2H2O+ 0.5O2 —> CaSO4.2H2O
role of catalytic converter and what catalyst is present
remove NOx and unburnt hydrocarbons
Pt or Rh (honeycomb structure)
2 equations for the workings of catalytic converters
2CO + 2NO —> 2CO2 + N2
C8H18 + 25NO —> 8CO2 + 12.5N2 + 9H20
fuel gases
- temp
- carbon chain
- uses
25degrees
1-4
calor gas, LPG
gasoline
- temp
- carbon chain
- uses
40 degrees
4-12
petrol for cars
naptha
- temp
- carbon chain
- uses
110 degrees
7-14
petrochemicals
kerosene
- temp
- carbon chain
- uses
200 degrees
11-15
jet fuel
disel oil
- temp
- carbon chain
- uses
300 degrees
15-19
fuel for disel engines
