Alkanes (topic 12)

What are the properties of Alkanes?

• almost non-polar

• Relatively non reactive (they burn and react with halogens under certain conditions

• Insoluble (unable to form hydrogen bonds with water molecules)

• Small alkanes are gases at room temperature

• Larger alkanes (18 carbons) are solids at room temperature

What is the formula for ring alkanes and why

C_(n)H_(2n)

There are no hydrogens on the end

What is the angle of a straight chain

109.5 degrees

What is the formula for a straight chain alkane

C(n)H(n+2)

What does the pollutant Sulfur Oxide cause

Photochemical Smog and Acid rain

Why are Sulfur Oxides Dangerous

They bond with the water vapour and the oxygen in the air to form sulfuric acid

What creates excess Carbon Dioxide

• Combustion

• to generate energy

Why is Carbon Dioxide dangerous

It is a greenhouse gas

what are Particulates and what do they do

• Carbon particles

• they exacerbate asthma and cause cancer

How is carbon monoxide formed and why is it dangerous

• Carbon monoxide is formed through incomplete combustion (when the reaction does not have enough oxygen)

• It is poisonous, bonds to the haemoglobin in your red blood cells and causes suffocation

What is the order of a chain reaction

• initiation

• Propagation

• Termination

What is fracking

A process done to collect natural gas from within the rocks

What are the pros of Fracking

• increase the supply of gas (reduces imported gas and electricity)

• Provides an alternative to coal

• Creates Jobs

What are the cons of fracking

• Local area may be disturbed (means that one needs a social license to operate)

• A large amount of water is used

• Chemical additives pollute the water supplies

• May cause earthquakes

• The methane combusts

What is the process of fracking

• Shale is drilled into and pressurised

• Water and sand are forced in to fracture the rock

• HCl and Methanol are also added to break up shale and prevent corrosion

• Gas is then collected

What are the two types of cracking

• catalytic

• Thermal

What are the conditions required for thermal cracking

High temperatures (700-1200K)

High pressure (7000 kPa / 70 atmospheres)

What are the conditions required for catalytic cracking

• Low pressure

• high temperature (720 K)

• a catalyst (zeolite)

What is produced within thermal cracking

A high portion of Alkenes are produced

How long is an alkane kept in the conditions for thermal cracking for and what happens if it is left in for too long?

• one second

• If left in for too long there will be too much decomposition