3.2 Alkanes

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Emma ;

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What are alkanes
Saturated hydrocarbons with the general formula CnH2n+2
What is the boiling point of an alkane dependent on?
The length of the chain as the longer the chain the greater number of electrons therefore stronger Van der Waals so the higher boiling points
What is crude oil?
Fossil fuels formed from the breakdown of plant and animal remains that have been subjected to high pressure
What is fractional distillation?
Will separate crude oil into different fractions?
What is a fraction?
A group of hydrocarbons that have a similar boiling point
Give an equation to show complete combustion of an alkane using propane?
C3H8(g) + 5O2(g) -> 3CO2(g) + 4H2O(g)
What does incomplete combustion of an alkane produce?
Carbon, carbon monoxide and unburned hydrocarbons
How do you remove sulfur dioxide from flue gases? Give equations.
Using calcium oxide or calcium carbonate

CaO(s) + 2H2O(l) + SO2(g) -> CaSO3(s) + 2H2O(l)
CaCO3(s) + 2H2O(l) + SO2(g) -> CaSO3(s) + 2H2O(l) + CO2(g)
What do catalytic converters do?
Remove gaseous pollutants from internal combustion engines by using precious metals spread over a mesh to form less harmful products such as N2, CO2 and H2O
What is cracking used for?
Converting longer chain hydrocarbons to more economically valuable shorter chain hydrocarbons
What is thermal cracking?
Alkanes are heated to high temperatures under high pressures. C-C bonds break and free radicals are formed. These react to form short chain hydrocarbons including at least one alkene
What are the conditions for thermal cracking?
High temperature (750 degrees Celsius)
High pressure of 70atm
What is catalytic cracking? 
Alkanes are heated to lower temperatures under lower pressures and passed over a zeolite catalysts consisting of SiO2 and Al2O3. This method is used mainly to produce motor fuels and aromatic compounds
What are the conditions for catalytic cracking?
Slight pressure
High temperature
Zeolite catalyst