chapter 12 - alkanes Flashcards
What is petroleum
Petroleum is commonly called crude oil, it is a complex mixture of hydrocarbons. It contains mainly alkenes, when it is first extracted from the ground it is useless. However the components of petroleum are useful as fuels. The mixture has to be separated into its components
Key points of the fractional distillation Column
The process relies on hydrocarbons having different chain length and boiling points.
Longer the chain the higher the boiling points therefore longer chain hydrocarbons will condense at the bottom of the column.
Each fraction is a mixture of hydrocarbons with similar boiling points
The crude oil is inputed into the column as a vapor
What are the conditions for thermal cracking
high temperature 400-900 degrees
high pressures 7000KPa
products - alkenes
uses- chemical feedstock
What are the conditions for catalytic cracking
High temperature 450degrees
slight pressure
zeolite catalyst
products formed - Branched alkanes, cyclo alkanes
uses - motor fuels
Why do we use cracking to break down alkanes
We break longer chain alkanes to form smaller more useful and more valuable molecules including shorter chain alkanes and alkenes.
What is complete combustion
Weather is an excess of oxygen
Products are carbon dioxide and water
exothermic reaction
What is incomplete combustion
Where there is a limited supply of oxygen
The products are carbon monoxide, or carbon (soot) and water
Carbon monoxide is a poisonous and potentially deadly gas
SULFUR containing impurities
S + O2 = SO2 fossil fuels contain S and when S combusts SO2 is formed
SO2 + H2O = H2SO3. has reacts with water in the atmosphere
FLUE GAS DESULFURISATION
acidic flue gasses are passed through a slurry or basic calcium oxide to form calcium sulfite. CaO + SO2 = CaSO3/ H2SO3 + CaO = CaSO3 + H2O
this is oxidised to calcium sulfate which is used as gypsum and plaster
CaSO3 + 0.5O2 + 2H2O = CaSO4.2H2O
What are problems with carbon monoxide (CO)
Carbon monoxide is formed from incomplete combustion. It is a deadly gas and binds to haemoglobin which is toxic.
Why is nitrogen monoxide and nitrogen oxide a dangerous gas (NO) & (NO2)
It is formed when nitrogen in the air reacts with oxygen in the atmosphere at high temperatures only
It’s can cause smoky fog, and it is irritating for asthma. This can cause raspatory issues
Why are unburnt hydrocarbons harmful and how are they formed
They are formed when the engine is not hot enough or insufficient enough
They are harmful as it creates a smog and triggers asthma which irritates the lungs.
Catalytic converter in engines
Nitrogen oxide and carbon monoxide are reduced in catalytic converters
What are the three catalysts used in a catalytic converter
Platinum, Palladium , rhodium
What are the equations that form from a catalytic converter
2NO + 2CO = N2 + 2CO2
What is a homologous series
They contain the same general formula
As you go down or up the homologous series the properties will generally follow a trend
have the same functional group
