Alkanes Flashcards
What are the steps for fractional distillation? (6)
- Crude oil is heated until it evaporates.
- Crude oil vapour is put into a fractionating column at the bottom and rises upwards.
- The temperature is highest at the bottom of the column.
- Long-chain hydrocarbons condense at the bottom
- Short-chain hydrocarbons have lower boiling points.
- They condense at lower temperatures nearer the top.
What causes acid rain
SO2 will dissolve in atmospheric water which produces acid rain
How are nitrogen oxides formed
- Nitrogen oxides form from the reaction between N2 and O2 inside the car engine.
- The high temperature and spark in the engine provides sufficient energy to break strong N2 bond
What environmental consequence does the pollutant NO and NO2 have
NO is toxic and can form acidic gas
NO2 is toxic and acidic and forms acid rain
What environmental consequence does the pollutant carbon dioxide have
Contributes towards global warming
What environmental consequence does the pollutant unburnt hydrocarbons have
Contributes towards formation of smog
What environmental consequence does the pollutant soot have
Global dimming and respiratory problems
What are the 3 main greenhouse gasses
Carbon dioxide (CO2)
Methane (CH4)
Water vapour (H2O)
Out of the three greenhouse gases name them in abundant order
Water CO2 CH4
Explain the greenhouse effect (4)
- UV wavelength radiation passes through the atmosphere to the Earth’s surface and heats up Earth’s surface.
- The Earth radiates out infrared long wavelength radiation.
- The C=O Bonds in CO2 absorb infrared radiation so the IR radiation does not escape from the atmosphere.
- This energy is transferred to other molecules in the atmosphere by collisions so the atmosphere is warmed.
Why have carbon dioxide levels risen
Burning of fossil fuels
What do Catalytic converts contain?
Converters have a ceramic honeycomb coated with a thin layer of catalyst metals platinum, palladium, rhodium– to give a large surface area
What do catalytic converters do?
Removes CO, NOx and unburned hydrocarbons (e.g. octane, C8H18)
from the exhaust gases, turning them into ‘harmless’ CO2 , N2 and H2O.
What are the three steps in free radical subsituition
Step one: Initiation
Step two: Propagation
Step three: Termination
What happens in the first step of FRS
The UV light supplies the energy to break the Cl-Cl bond. It is broken in preference to the others because it is the weakest.
Cl2 –> 2Cl*
What is a free radical
A reactive species which possesses an unpaired electron.
How are free radical represented
Free radicals do not have a charge and are represented by a *( not actually an asterisk just a black circle)
What happens at Step two: Propagation
The chlorine free radicals are very reactive and remove an H from the methane leaving a methyl free radical
CH4 + Cl. —> HCl + .CH3
.CH3 + Cl2 –> CH3Cl + Cl.
The methyl free radical reacts with a Cl2 molecule to produce the main product and another Cl free radical
All propagation steps have a FreeRadicalInTheReactantsAndInTheProducts.
What happens as the Cl free radical is regenerated?
Regenerated= Cl gets a free radical again
It can react with several more alkane molecules in a chain reaction.
How is crude oil formed
From the remains of plants and animals from millions of years ago that have undergone high pressures and temperatures
What are alkanes
Saturated hydrocarbons with the general formula CnH2n+2
What is a use of alkenes
Prpoduction of plastics
What is flue gas desulphurisation
Neutralising Sulphur dioxide by reacting it with calcium oxide (SO2+CaO–>CaSO3)
add oxygen to caso3–> cas04 is useful as it can be used in plastering
How do nitrogen oxides form
The engine of a car reacts with nitrogen and oxygen in the atmosphere with heat and pressure forming 2NO
