6.2 Flashcards
what happens in fractional distillation
Crude oil is heated in a furnace Which time is it into vapour which passes into column
what is inside the fractioning column
There is a temperature gradient.
It’s hotter at the bottom and cooler at the top.
what happens once crude oil vapour enters the fraction column
The vapour then reached the faction, which is slightly higher than its BP, causing it to condense.
what is the extra step to fractional distillation
Some hydrocarbons reach the top without condensing. These then undergo further fractional distillation separately.
what is cracking
the process of converting long chain hydrocarbons into smaller ones and also forming an alkene
what are the steps of cracking
The hydrocarbons are passed in the heavier fractions through a heated catalyst (usually zeolite).
This causes the hydrocarbons to break into smaller alkane + alkene and sometimes hydrogen is also produced.
What is reforming
turning straight hydrocarbon chains into cyclic
how does reforming happen
Hydrocarbons are heated with a catalyst usually platinum.
This makes it more cyclic and have more branches.
what is complete combustion
Reaction where a molecule is reacted with oxygen (when there is a plentiful supply) to form CO2 + H2O and all atoms are fully oxidised.
what is incomplete combustion
Reaction with insufficient oxygen to produce carbon monoxide as well as water and carbon in solid form. Some atoms are not fully oxidised.
what is carbon monoxide
A colourless + odourless gas that prevents transportation of O2 in the body.
how are oxides of sulphur formed
A colour + odourless gas that prevents transportation of O2 in the body.
how do these oxides contribute to acid rain
Both these gases dissolve in the water rand form sulphuric acid which contributes to acid rain.
what damage do these cause
damage to aquatic live, damage to crops + forest.
how are oxides of nitrogen formed
Few alkane molecules contain nitrogen.
When nitrogen undergoes combustion, it forms oxides of nitrogen (NOx)
how is nitrogen monoxide formed
N+O2 = 2NO (nitrogen monoxide
how is nitrogen dioxide formed
2NO + O2 = 2NO2 (Nitrogen dioxide)
how is nitric acid formed
2NO2 + H2O = HNO2 +HNO3 (nitrogen acid +nitric acid)
how do catalytic converters work
Fitted in a cars exhaust system to reduce pollution
Made of small quantities of precious metals which are spread thinly over a honeycomb mesh (to increase the S.A for reaction).
It oxides the pollutants.
equations in catalytic converters
2CO +O2 = 2CO2
2NO + 2CO = N2 + 2CO2
what are biofuels
Biofuels are obtained from living matters which died recently.
what are the 2 types of biofuels
Biodiesel
Bio-alcohal
what is biodiesel
Biodiesel is a fuel made from vegetable oil obtained from plant.
what is bio-alcohal
Fuels made from plant matter often using enzymes or bacteria
land use, yield, manufacture/transport, carbon neutrality of biofuels
Land use = a lot of land is needed meaning it compromised land for food.
Yield = low but it is gradually increasing.
Manufacture/ transport = NO exploration or drilling cost. Substantial cost in growing, processing and transport.
Carbon neutrality=is low
Land use, yield, manufacturing/transport, carbon neutrality of natural gas
Natural gas
Land use = no land needed as it comes from underground.
Yield=very high
Manufacturing/transport=Exploration and drilling cost is high. Low processing cost. Transport cost is low by pipeline.
Carbon neutrality-not carbon neutral
what is a substitution reaction & formula equation
A reaction where an atom or group is replaced by another atom or group
CH4 + Cl = CH3Cl + HCL
what is a mechanism
a sequence of steps in an overall reaction. Each step shows what happens to the electron involved in the bond breaking or bond formation
\What is a radical
a species that contains an unpaired electron
what is homolytic fission
is the breaking of a covalent bond where each of the bonding electrons leaves with one species forming a radical
what happens in initiation
& formula example
involved the formation of radicals due to a bond breaking caused by U.V
Cl2 = Cl. + Cl.
what happens in propogation & example
reaction between one free radical and a normal molecule to produce another free radical and one molecule.
Cl. + CH4 = CH3. + HCL then
CH3. + Cl2 = CH3Cl + Cl.
what happens in termination & examples
2 radicay6huls react to form a molecule
Cl. + Cl. = Cl2
Cl. + CH3. = CH3Cl
CH3. + CH3. = C2H6
what are the bonds in a double bond
Sigma
pi
what is a sigma bond
a covalent bond that’s formed when 2 s orbitals overlap horizontally/ axially ( end - on)
what happens in a sigma bond
a strong electrostatic force of attraction is formed between nuclei and shared electrons due to high electron density between nuclei
what is pi bond
covalent bond is formed by parrallel overlap of 2 p orbital lobes sideways.
why is sigma bond stronger
sigma bonds are stronger as there is a higher electrons density which is spread out over a smaller area ( only between nuclei ) the electrostatic attraction is higher and therefore have higher bond enthalpy
why are double bonds more reactive than single
pi bonds are more reactive as they are spread out over a large area. Due to the high electron density it attracts many electrophiles causing it to react with many compounds
what is an addition reaction
reactin in which 2 molecules become 1 by combining
what is hydrogenation
an addition reaction in which hydrogen is added to an alkene to form an alkane .
what is used in hydrogenation
a nickel catalyst
what is an example of hydrogenation
manufacturing of margarine.
- veg oils are unsaturated and reacted with hydrogen to turn it into margarine.
why do they do this
margarine is a healthier option
what is halogenation
reaction where a halogen is added
what is hydration
reaction where H2O is added
how does this reaction happen
Takes place by heating alkene with steam and passing the mixture over a catalyst of phosphuric acid.It forms an alcohal
what is an electrophile
a species that is attracted to a region of high energy electron density
Electrophilic addition
reaction where 2 molecules form 1 and the attacking molecule is an electrophile
hetrolytic fission
breaking of a covalent bond so both bonding electrons are taken by one atom
what is polymerisation
A process where small molecules called monomers join together into larger molecules called polymers that consist of repeating molecules
what is addition polymerisation
All the atoms in the monomers are used to form polymer
what is condensation reaction
Monomers join up with the expulsion of small molecules while not every origional atoms are present within the polymer
What is a repeating unit
The set of atoms that are joined together in large numbers to produce the polymer structure
why are polymers used
- manufactured on a large scale with variety
- Light
- Cheap
- Unreactive so they can be used to make many things
what does biodegradable mean
can be broken down by microbes
are polymers biodegradable or non-biodegradable
non-biodegradable
how does Reduce usage of polymers help
Reducing polymer use unecessarily by dicouraging free plastic bags + using bags for life.
how does recycling help
The polymers are turned into other materials and
what are the 2 stages of recycling
- sorting polymers so it can be processed together effectively and appropiately
- Process it by chopping waste into small pieces + washing it and turning it into new material by; melting, mouldering, fibre production
how does chemical feedstock help
breaking polymers into gasses to produce a feedstock that can be used in other chemical reactions
how does incineration help
Takes polymers and converts into heat energy to generate electricity
by is incineration bad
some polymers contain toxic metals ( which are used to pigment polymers ) which when burnt form toxic gasses.
how does producing biodegradable polymers help
using polymers that are biodegradable
how is this also bad
they are made from plant matherial which requires huge land space to grow + when they are broken down they release hydrogen + carbon atoms that can’t be used
