Alkanes Flashcards
What is an alkane
A saturated hydrocarbon with the general formula CnH2n+2
What is the general formula for alkanes
CnH2n+2
What is the general formula for cycloalkanes
CnH2n
What does a saturated hydrocarbon mean
Means that each carbon is bonded 4 times with the maximum number of hydrogens possible
Are cycloalkanes saturated or unsaturated
Saturated
What is crude oil
A mixture of different length hydrocarbon
What temperature are hydrocarbons heated to in a fractional distillation column
350 degrees C
Where is it coolest in a fractional distillation column
Coolest at top
Hottest at bottom
Give 1 use of Gas (top of fractional distillation column)
Used in LPG and stove gas
Give 1 use of Bitumen
Roofing and tarmac
Give 1 use of kerosine
Jet fuel
Give 1 use of fuel oil
Ships and power station
What is cracking
Breaking a longer chain alkane into a shorter chain alkane and an alkene
What are the conditions for thermal cracking
1000 degrees C
70atm
What are the main products of thermal cracking
Alkenes
What are the conditions for catalytic cracking
450 degrees C
Zeolite catalyst
Moderate pressure (150kPa)
What are the main products of catalytic cracking
Aromatic hydrocarbons
What are Aromatic hydrocarbons useful for
In fuels for vehicles
What is an Aromatic hydrocarbon
Hydrocarbons which contain benzene rings
Why do we use a zeolite catalyst for catalytic cracking
Lowers temperature and pressure needed for cracking to occur and so lowers cost and speeds up the process
What do alkanes form when they combust completely
CO2 and H2O
Why are alkanes good fuels
Most of them burn readily to produce large amounts of energy
What are two negative products from incomplete combustion of alkanes
Carbon monoxide
Soot (C)
Why is CO poisinous
Bonds to haemoglobin in the blood and prevents oxygen from bonding
How can CO be removed in a vehicle
Catalytic converter
Give 3 hazards with soot
causes breathing problems
Makes buildings dirty
Clogs up engines
What is the greenhouse effect
When greenhouse gasses absorb infra red radiation (heat) from the sun but emit some back to earth
What 3 things mix to form ozone
Sunlight
Hydrocarbons
Nitrogen dioxide
Where does ozone occur
The lowest level of the atmosphere
When does photochemical smog occur
When carbon particulates and ozone mix
What is a hazard with photochemical smog
Harms respiratory system in humans and animals
When are oxides of nitrogen formed
When nitrogen and oxygen found in the air combine under high temperature and pressure for example in car engines
What is the role of a catalytic converter
Help to reduce the amount of of unburnt hydrocarbons and oxides of nitrogen going into the atmosphere
How can the burning of fossil fuels contribute to sulfur dioxide in the atmosphere
When some fossil fuels containing sulfur impurities are burned, the sulfur reacts with oxygen producing sulfur dioxide
How does sulphur dioxide in the atmosphere contribute to acid rain
Sulphur dioxide reacts with water in the atmosphere to for sulphuric acid which falls as acid rain
What type of gas in sulphur dioxide
An acidic gas
What process can we use to remove sulphur dioxide from flue gasses
Wet scrubbing
What is wet scrubbing
Dissolving calcium carbonate or oxide in water and spraying on acidic sulphur dioxide gas
What are the 3 stages in Free radical substitution
Initiation
Propagation
Termination
What is the initiation stage in free radical substitution
Radicals produced using UV
Bond breaks producing 2 radicals
What is the propagation stage in free radical substitution
When a radical reacts with a non radical molecule
New radicals are then created
What is the termination stage in free radical substitution
When 2 radicals react to form a non radical molecule
What is photodissociation
When sunlight breaks a bond
What is the equation for the initiation stage in the free radical substitution of methane and chlorine (CH4 + Cl2—-> CH3Cl + HCl)
Cl2 (UV) —–> 2.Cl
What are the 2 equations for the propagation stage in the free radical substitution of methane and chlorine (CH4 + Cl2—-> CH3Cl + HCl)
.Cl + CH4 —> .CH3 + HCL
.CH3 + Cl2 —-> CH3Cl + .Cl
What is the equation for the termination stage in the free radical substitution of methane and chlorine (CH4 + Cl2—-> CH3Cl + HCl)
.Cl + .CH3 —>CH3Cl
What is the similarity between the 2 equations in the 2 propagation steps in free radical substitution
The radical on the reactant side of the first equation must be the radical on the product side of the second equation
What happens if we have excess of the radical in the termination step in the formation of a haloalkane in free radical substitution
We will get a di,tri,tetra haloalkane
