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Crude Oil
Mixture of hydrocarbons with different boiling points.
Hydrocarbon menaing
Compound made of hydrogen and carbon only
Saturated meaning
Alkanes consist of single carbon carbon and single carbon hydrogen bonds only.
Fractional Distillation
Crude oil heated until it evaporates, vapor moves up the column (w/ diff condensation points)
Vapor condenses and is collected in column
Short hydrocarbons condense as top due to low BP
Long hydrocarbons condense at bottom due to high BP
What is petroleum
Mixture consisting of mainly alkane hydrocarbons that can be serrated by fractional distillation
What kind of change does fractional distillation provide?
Physical change
What catalyst is needed for fractional distillation?
Zeolite catalyst
What happens if there are weaker forces in the fractional distillation
lower MP and BP,
lower vDw, and less surface contact
Useful products of fractional distillation?
Petrol
Petroleum gas
kerosene
diesel
lubricating oil
heavy fuel oil
bitumen
Cracking
Long chain hydrocarbons broken down into smaller chain useful hydrocarbons.
Breaks C-C bonds
What type of change is cracking
Chemical change
Cracking Formula
long chain alkane (less useful) —> smaller alkane (fuels) + alkene(s) (making plastic/polymers) + hydrogen (Sometimes) (more useful)
Types of cracking
Thermal
Catalytic
Thermal Cracking
High temp (700 - 1200K)
High pressure (up to 7000kPa)
forms alkane and alkenes
Catalytic Cracking
Zeolite catalyst
High temp (720K)
Slight pressure
forms branched hydrocarbons and aromatic hydrocarbons
Why is high temp needed for cracking
so C-C bonds can break
Why do less people use catalytic cracking?
Zeolite catalyst expensive
Branched hydrocarbons are less useful
What happens in the covalent bond in thermal cracking?
one electron from the pair in the covalent bond goes to each carbon
economic reasons for cracking
solves the mismatch between supply and demand for short chain alkanes. A greater amount of short chain alkanes is required than is found in crude oil. Cracking produces smaller chained, more useful alkanes from less useful longer-chain alkanes.
Why are alkanes good fuels?
strong, non polar, C-C and C-H bonds making them stable(unreactive)
when C-C and C-H bonds broken lots of heat energy is needed
Complete combustion eq
fuels (alkanes) + oxygen —> carbon dioxide + water
What type of reaction is combustion?
exothermic
When is more oxygen needed in complete combustion?
Higher chain length
Incomplete combustion eq
Alkane + Oxygen —> Carbon Monoxide + Water
Alkane + Oxygen —> Carbon + Water
When does incomplete combustion happen?
when oxygen presence is limited
Why are the products of incomplete combustion bad?
C is solid - causes global warming as soot
H2O is gaseous
CO (carbon monoxide) hazardous, colorless, odorless and causes death
When is nitric oxide produced?
in car engine under high heat and pressure
Nitric Oxide production eq
2NO + O2 —> 2NO2
4NO2 + 2H2O + O2 —> 4HNO3
Why is nitric oxide hazardous?
combine with rain water forming acid rain
What stops exhaust gases from leaving the atmosphere?
Catalytic converters
Catalytic converters
Composed of ceramic honey comb containing thin layer if metals like platinum, rhodium or palladium designed to remove CO, NO and hydrocarbons from car exhausts.
Catalytic converters eq
2CO + 2NO —> 2CO2 + N2
What pollutants does a internal combustion engine produce?
NOx, CO, C and unburned hydrocarbons
How does the internal combustion engine produce a number of pollutants?
through combustion reactions that release harmful chemicals into the atmosphere
Why is sulfur bad?
combines w/ oxygen to produce sulfur dioxide
this reacts with water producing weak sulfuric acid (acid rain)
Sulfur acid rain eq
SO2 + H2O + 1/2O2 —→ H2SO4
Acid Rain Effects
Damaged architecture
Corrode infrastructure
Kills aquatic life
Kills plants and wildlife
Destroys habitats
Removal of sulfur
Desulphurisation
Desulphurisation
Sulfur dioxide can be removed from power stations using calcium carbonate to calcium sulfite
Desulphirication eq
CaCO3 (s) + SO2 (g) —> CaSO3 (s) + CO2 (g)
How is a haloalkane formed
alkane with one or more H replaced by halogen by free radical substitution in the presence of UV
Free Radical Substitution
Alkane + X2 —> Haloalkane + HX
Free Radical Substitution C2H6 and Cl
C2H6 + Cl2 —> C2H5Cl + HCl
The stages of free radical substitution
Initiation
Propogation
Termination
Free Radical
Species with an unpaired electron formed when a covalent bond is broken
extremely reactive
Homolytic fission
Each atom takes one electron
Cl2 —> Cl⋅ + Cl⋅
Heterolytic fission
XY —> X⋅ + Y⋅
Initiation
if it was chlorine
Cl2 —> Cl⋅ + Cl⋅ via homolytic fission
Propogation
Alkane reacts with free radical, loses H
if it was the CHLORINATION OF METHANE
Possibility 1. CH4 + Cl⋅ —→ HCl + CH3⋅
Possibility 2. Cl2 + ⋅CH3 —→ CH3CL + ⋅Cl
why is the halogen always broken first in propogation
Cl - Cl (eg) always weakest bond
Termination
free radical joins with another
Possibility 1. Cl⋅ + Cl⋅ —> Cl2
2 . Cl⋅ + CH3⋅ → CH3Cl
3. ⋅CH3 + ⋅CH3 —> C2H6
CHLORINATION OF METHANE
Ozone Layer
Thin part of gas (O3) that absorbs almost all of the suns harmful UV
Ozone Layer Benefits
Prevents harmful UV reaching life
Decreases chance of getting cancer from UV
What is ozone an allotrope of?
Oxygen gas
What makes ozone?
Naturally or by photocopiers and laser printers
Ozone formation
Naturally occurring O2 molecules bombarded by high energy UV from the sun, breaking them into radicals (O•)
O• reacts with more O gas making ozone molecules.
Ozone Formation Radical
O2 → 2O•
2O• + 2O2 → 2O3
3O2 → 2O3
Ozone depletion
Ozone layer gets thinner due to CFC
CFC
Organic molecule with chlorine, fluorine and carbon
Why did CFC lead to ozone depletion?
They were everywhere (refrigerators, aerosol propellants and polystyrene)
Cheap and nonflammable
CFC is banned in the
UK
Why wasn’t CFC banned before in the UK
Not enough evidence of ozone depletion
Lack of CFC alternatives
Hard to obtain international agreement
Commercial CFC use
