Organic Flashcards
What increases the boiling point of alkanes and why?
- The longer the carbon chain, the higher the boiling point due to stronger Van der Waal’s forces between molecules
- More branched carbon chains will have a lower boiling point as the molecules can’t pack close together so the Van der Waal’s forces are weaker
What is crude oil formed from?
The slow decay of marine animals and plants over millions of years under heat and pressure
What is the process of fractional distillation?
- The crude oil is vaporised
- The vapour is passed into a fractionating column which is hot at the bottom and cold at the top
- As the vapour rises, it cools and will condense at different fractions of the column as they have different boiling points
- The larger the molecule with a higher boiling point, the lower down the column it condenses
What can the residue from primary distillation be used for?
Fuel oil, lubricating oil, waxes and bitumen
Why is cracking useful?
Because there is a higher demand for short chain molecules that can be used for petrol and useful fuels
What is cracking?
The thermal decomposition of alkanes to produce higher value shorter C-chain products
What are the conditions required for thermal cracking?
900°C
70 atm
What does thermal cracking produce?
Alkenes
What are the conditions required for catalytic cracking?
450°C
1-2 atm
What type of catalyst is used in catalytic cracking?
A zeolite catalyst
What are the products of catalytic cracking?
Motor fuels e.g. cyclic alkanes, branched alkanes and aromatics
What are the problems with releasing CO2, CO and C?
CO2 is a greenhouse gas
CO is toxic
C can cause respitory problems and global dimming
What are the problems caused by releasing SO2 and NO/NO2?
They cause acid rain
What is flue gas desulfurisation?
When SO2 is removed from the waste gases in furnaces
How does flue gas desulfurisation work?
The gases pass through a filter containing calcium oxide or calcium carbonate
What are the possible reactions of flue gas desulfurisation?
CaO + SO2 –> CaSO3
or
CaCO3 + SO2 –> CaSO3 + CO2
What do catalytic converters do?
They remove CO, nitrogen oxides and unburned hydrocarbons from the exhaust gases, turning them into CO2, N2 and H2O
What are the reactions in a catalytic converter?
2CO + 2NO –> 2CO2 + N2
C8H18 + 25NO –> 8CO2 + 12½N2 + 9H2O
What are greenhouse gases?
Gases that absorb the IR radiation given off by the earth but do not absorb the UV radiation given off by the sun
These gas molecules will contain polar bonds as it’s these bonds that absorb IR radiation and vibrate
What happens in the initiation stage?
You start with a halogen that becomes two free radicals
What is required for the initiation stage to occur?
UV light
What happens during the propagation stage?
A molecule and a free radical react to form a different molecule and free radical
What happens during the termination stage?
Two free radicals make a molecule
What is the problem with chlorofluorocarbons (CFCs)?
They damage the Ozone layer
How do CFCs damage the ozone layer?
- CFCs rise to the stratosphere
- UV light provides energy to break C-Cl bonds
- Cl radicals are formed
What is the chain and overall reaction of Cl• destroying O3 molecules?
Cl• + O3 –> ClO• + O2
ClO• + O3 –> Cl• + 2O2
Overall
2O3 –> 3O2
