3.3.2 Alkanes Flashcards
Are alkanes saturated or unsaturated
Saturated
Thermal cracking
Condition + products
- high pressure and temperature
- lots of alkenes - used to make polymers
Catalytic cracking
Catalyst, conditions & products
- Zeolite catalyst
- slight pressure & high temperature
- aromatic hydrocarbons and alkanes
Complete combustion is when
There is sufficient supply of oxygen
Products of complete combustion
Water and co2
Incomplete combustion is when
There is a limited supply of oxygen
Products of incomplete combustion
Carbon monoxide (CO) and water
Why is carbon monoxide bad
Toxic
Binds to haemoglobin so prevents oxygen being carried round the body
Why is soot bad
Causes respiratory issues
How are nitrogen oxides formed
High pressure & temperature cause the nitrogen and oxygen atoms in the air to react together
Nitrogen monoxide
Reaction between carbon monoxide and nitrogen monoxide
2CO + 2NO —> 2CO2 +N2
What are the 3 pollutants from a cars exhaust
Nitrogen oxides
Unburnt hydrocarbons
Carbon monoxide
Reactions of a catalytic converter to remove the 3 pollutants from a cars exhaust
2 things to remember
1) complete combustion of a hydrocarbon
E.g. C3H8 +5O2 —> 3CO2 + 4H2O
2) 2NO —-> N2 + O2
3) 2NO + 2CO —> N2 + 2CO2
Include state symbols
All of them are gases
What are the 3 steps of free radical substitution
Initiation step
Propagation step
Termination step
What is needed for free radical substitution to occur
Ultra violet light
Are alkanes reactive or in reactive + why x2
Unreactive
Non polar (carbon + hydrogen similar electronegativity)
Bonds are relatively strong (lots of energy to break)
What is a free radical
Any species with an unpaired electron
This is the initiation step
Cl-Cl—> *Cl + *Cl
But what is the name for this reaction of the bond breaking
Homolytic Fission
What would you do to prevent further substitution
Use an excess of the alkane E.g. methane
To prevent further substitution
Cracking produces …
An Alkene and alkane
Formula of soot
C
Why is soot bad for car
Builds up in the engines so car does not work properly
Why is sulphur dioxide bad
Causes acid rain
How is the issue of sulfur dioxide resolved
The sulfur dioxide is removed from flue gases by wet srubbing
An alkali E.g. calcium carbonate is used to neutralise the sulfur dioxide
