3.2 Alkanes Flashcards
What is an alkane?
A saturated hydrocarbon containing only C-H bonds
What is the general formula of an alkane?
C2H2n+2
Are akane bonds polar?
No - Carbon and Hydrogen have similar electronegativities
What intermolecular forces do alkanes have?
Only Van der Waals
Are alkanes soluble in water?
No
Name the fractions in a fractionating column in order of high to low bp and then name their uses.
- Gases - canister fuels
- Petrol - Cars
- Kerosene - Jet fuel
- Diesel oil - Lorries/cars
- Lubricating oil - candles, engine oil
- Fuel oil - Ships, power stations
- Tar/Bitumen - roads/roofing
What happens during the fractional distillation of crude oil?
- The crude oil is heated unit it is mostly vaporised
- Passed into a fractionating column that is cooler at the top than it is at the bottom
- Vapour rise up the column and condense at different points - this is collected
- The shorter the chain the higher up it condenses
How is the fracking of natural gas carried out?
- Natural gas held within shale rock
- Drill into shale, forced pressurised water and sand into rock to fracture it, collect gas
- HCL and methanol added to break up shale and prevent corrosion
What are some advantages of fracking?
- Gas supply for many years
- Reduces imported gas and electricity
What are some disadvantages of fracking?
- Lots of traffic to local area
- Concern about amount of water used
- Chemical additaves can pollute water supplies
- Small earthquakes
Why are alkanes cracked?
To turn a long chain alkane, which is not economically valuable into more economically productive shorter one
What are the conditions for thermal cracking?
- 700-1200K
- Up to 7000kPa
What are the main products of thermal cracking?
Alkenes
What are the conditions for catalytic cracking?
- Lower temperature (720K)
- Lower Pressure (but above atmospheric)
- Zeolite catalyst
- Honeycomb structure
What are the main products of catalytic cracking?
- Cycloalkanes
- Aromatic Hydrocarbons
- Branched alkanes
