3.2 Alkanes Flashcards Preview

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Flashcards in 3.2 Alkanes Deck (20):

What is petroleum?

A mixture of Alkane hydrocarbons that can be separated by fractional distillation


What is cracking?

The process of breaking non useful Alkane hydrocarbons into shorter hydrocarbons by breaking c-c bonds.


What is thermal cracking?

Cracking produced at high temperatures and high pressures (1000c; 70Å)
Lots of Alkenes are produced


What is catalytic cracking?

Cracking using a zeolite catalyst (very high surface area), and a slight pressure and high temperature (500c)
Creates aromatic compounds and motor fuel Alkanes


What are the benefits of catalytic cracking?

Lower pressure is cheaper and safer
Lower temperature is cheaper
Speeds up the reaction and saves time


What are the benefits of thermal cracking?

Produces more Alkenes and polymer Alkenes.


What is complete combustion of Alkanes?

When an Alkane is burned in excess and sufficient amount of oxygen to produce carbon dioxide and water.


What is incomplete combustion of Alkanes?

Alkanes burned in a shortage of supply of oxygen or when the Alkane is in excess. This produced carbon monoxide and water and/or traces of carbon


Why is carbon monoxide a pollutant?

It is toxic to the body as it replaces oxygen on haemaglobin in the blood stream


How is carbon dioxide a pollutant?

It is a green house gas which absorbs infra red and emit some of the energy back to earth, heating the surface.


How is carbon a pollutant?

It blackens buildings, causes respiratory issues, and global dimming


What is SO2 or sulfur dioxide?

In impure fuels there are traces of sulfur. When burned these oxidise and the compound can cause acid rain when dissolved in the moisture.


How can we remove sulfur dioxide?

This is called desulfurisation. Flu gases mix with an alkaline slurry and forms a harmless salt

ie) CaO + SO2. -> CaSO3


How are NO, NO2 and other similar nitrous oxides, pollutants?

Reaction of N2 in impure fuels with O2 at high temperatures (in engines and furnaces) form these compound which then can cause acid rain when dissolved by the moisture.


What are catalytic converters?

They have large surface areas and are coated in materials to trap the pollutants.


Chlorination of Alkanes:
What is initiation?

Cl2 --UV--> 2Cl•


Chlorination of Alkanes:
What is propagation?

Cl• + CH4 --> •CH3 + HCl

•CH3 + Cl2 --> CH3Cl + Cl•


Chlorination of Alkanes:
What is substitution?

In Cl2 excess all H can be replaced
CH4 + Cl2 -> CH3Cl + HCl

CH3Cl + Cl2 -> CH2Cl2 + HCl

CH2Cl2 + Cl2 -> CHCl3 + HCl

CHCl3 + Cl2 -> CCl4 + HCl


Chlorination of Alkanes:
What is termination?

•CH3 + Cl• -> CH3Cl

•CH3 + •CH3 -> C2H6

Cl• + Cl• -> Cl2

Two radicals can recombine


What are Alkanes?

Saturated hydrocarbons with the general formula of CnH2n+2