C12-alkanes Flashcards
what is a hydrocarbon
compound containing only hydrogens and carbons
what is a saturated hydrocarbon
only contains single bonds between carbon atoms
what is the general formula for an alkane
Cn+H2n+2
name the first 4 alkanes
methane
ethane
propane
butane
what si the trend in boiling points in alkanes
as chain length increases the boiling point increases
why are hydrocarbons non polar
the electronegativity difference between carbon and hydrogen is very small
what tyoe of IMF exists between hydrocarbon chains
van der waals
why do branched chains have lower melting points
smaller surface areaso fewer VDW attractions
how are mixtures of hydrocarbon seperated
feactional distillation
what dies the word immisible mean
does not mix
what is crude oil
a mixture of different hydrocarbons
what is a fraction?
a group of compounds woth similar boiling points that are removed at the same lvl of the fractionatijg column
where are smaller hydrocarbons collected
near the too of the fractionating column
why do small chains have lower boiling points
less atoms in the chain so less VDW forces between then
what happens in cracking?
long hydrocarbons are converted into smaller hydrocarbons
why is cracking useful
shorter hydrocarbons are more useful
name two tyoes of cracking
thermal and catalytic cracking
gove the conditions for thermal cracking
1000-1200 K and upto 70 atm
what is the time frame for thermal cracking
1s
why is thermal cracking so short
to orevent complete decomposition of the hydrocarbon
what catalyst is used in catalytic cracking
a zeolite
what is a zeolite
an acidic mineral with a honeycomb structure made from aluminium oxide and silicon dioxide
what are the conditions for catalytic cracking
800-1000 K 1-2 atm zeolite catalyst
what is the purpose of the honeycomb structure
to increase surface area and so rate if reaction
whats the time frame for catalytic cracking
2-4s
what is produced in thermal cracking
high percentage of alkenes and some shirt alkanes
what is peoduced in catalytic cracking
mainly aromatic hydrocarbons and motor fuels
what is required for complete combustion
excess amount of oxygen
what is a major component of natural gas
methane
what is the major component of liquid petroleum gas
butane
what is formed in incomplete combustion
carbon monoxide and water
give three properties of carbon monoxide
toxic
colourless
odourless
why is carbon minoxide toxic
binds to heamoglobin in red blood cells preventing them from carrying oxygen
what is soot
carbon particulates
what are the four stages of internal combustion engine
intake
compression
combustion
exhaust
how is the fuel ignited in an internal combustion engine
extreme temperature spark
what tyoe of pollution is caused by CO
toxic gas
what pollution is caused by C
particles exacerbate asmaa
what pollution is caused by SO2
acid rain
what pollution is caused by NOx
acid rain and photochemical smog
what pollution is caused by hydrocarbons
react woth NOx to form geound lvl ozone which leads to resporatory problems
why is greenhouse effect so important
wothout it, earth would be too cold to support life
how is the CO2 in the atmosphere produced
respiration and combustion
gow is the methane in the atmosphere produced
byproduct of sheep and cattle farming
ph of normal rainy water
5.5
why is rain water a weak acid
CO2 present in the atmosphere
what pH is acid rain
lower than 5.5
what problems does acod rain have
destroys trees and vegetation
corrodes buildings and kills fishes in lakes
what causes photochemical smog
toxic gases and minute solid oarticles suspended in air
when is smog formed
when NOx, SO2 or unburnt hydrocarbons react with sunlight
what health problems are associated with smog
irritated eyes
nasal congestion
emphysema
what is the purpose of a catalytic converter
converts toxic compounds from the internal conbustion engine into kess harmful products
what is a catalytic converter made of
a cermaic honeycomb covered in a thin layer of platinum and rhodium
what is the process used to remove sulfur compounds from combustion emmisions called
flue gas desulfurisation
what happens in flue gas desulfurisation
gasses are passed theough a wet slurry of CaO or CaCO3
what do the CaO or CaCO3 do in flue gas desulfurisation
neutralise the acidic SO2
1) what is the products of flue gas desulfurisation
2) what are they converted into
1) calcium (IV) sulfate (calcium sulphite)
2) calcium (VI) sulfate
what is calcium (VI) suldate used for
construction
what does [0] represent
oxygen from an oxidising agent