3.2 alkanes

What is cracking?

Cracking is when long chain hydrocarbon are converted to smaller hydrocarbon chain by breaking the C-C bond

What are some economic reasons for cracking long hydrocarbon chains?

Shorter hydrocarbon chains are more in demand + more valuable

Conditions for thermal cracking + what do they produce ?

• High pressure around (7000KPa)

• High temperature (400C to 900C)

• Produces alkanes and alkenes

Conditions for catalyctic cracking + products?

• slight/moderate pressure

• High temp 450

• Zeolite catalyst

• Produces branched, cyclic alkanes and aromatic hydrocarbons

Complete combustion?

• Happens in excess O2

• Products are CO2 and H20

Incomplete combustion?

• Occurs under a limited amount of O2

• Products are CO and/or C

Which combustion releases the most energy?

Complete combustion produces more energy per mole than incomplete

State how nitrogen monoxide and nitrogen dioxide is produced

Car engine → high temp + sparks →forming nitrogen monoxide and also nitrogen dioxide

What does unburnt hydrocarbons do?

They form ground level ozone → production smog → causing lung cancer, eye irritation and respiratory problems

consequence of soot?

Causes global dimming

Consequences of nitrogen dioxide and sulfur dioxide

Contributes to acid rain, kills crops, kills fishes as it contaminates water

Give the formula used to help remove sulphur dioxide from the combustion process

CaO or CaCO3

1. What are the steps for free radical substitution?

1. Initiation

2. Propagation

3. Termination

What happens at initiation ?

Uv supplies energy to break the covalent bond between Cl-Cl

What happens during propegation ?

Cl* is very reactive, therefore it removes H from methane, turning it into a methyl free radical

What happens during termination?

What does carbon neutral mean?

No net emissions of CO2 In the atmosphere

Why is fuel no carbon neutral

Due to fossil fuel use during processing