Production of Materials Flashcards
what is the most important hydrocarbon used in the petrochemical industry?
ethene or ethylene
what is the chemical formula for ethylene?
C2H4
what are some properties of ethylene?
- alkene (unsaturated)
- low MP and BP
- Insoluble in water
- carbon double bond is a region of high electron density
where does ethylene usually come from?
via cracking large hydrocarbons sourced from fractionally distilling crude oil
what is cracking ?
cracking is the process in which large, long chain hydrocarbons are broken up into smaller and more useful hydrocarbons
why would some hydrocarbons get cracked?
most large hydrocarbons are in low demand, unlike short chain hydrocarbons, thus for profit these large hydrocarbons are cracked to form smaller more profitable hydrocarbons
why is ethylene so special?
because it holds unlimited potential on in the petrochemical (plastics) industry due to its versatility and the variety of reactions and compounds it can undertake in and make respectively
what are the three forms of cracking ?
steam cracking
thermal cracking
catalytic cracking
what does catalytic cracking entail?
catalytic cracking ulitises a zeolite catalyst to lower the temp required to extract these useful components when cracking
what are the properties of the zeolite catalyst used in catalytic cracking?
- high surface area
- Porous
- selective
what are the conditions required for catalytic cracking ?
- atmospheric pressure
- absense of air
- temps at approx 500 degrees celcius
what is the difference between a saturated and unsaturated hydrocarbon ?
saturated
contains only single bonds, and no more atoms can be added to it
unsaturated
contain double or even triple bonds, allowing additional parts to join the chain
why are alkenes much more reactive than alkanes?
an alkenes double bond makes it inherently more unstable as it is a region of high electron density and thus can break apart more readily than an alkanes single bonds
why is ethylene so reactive?
because of its double bond and how it is a region of high electron density with the ability to attract electronegative species such as halogens and thus create many other different compounds as a result
what are the four main types of addition reactions which ethylene commonly participates in?
hydrogenation- heated with hydrogen with a catalyst
halogenation- halogens react with ethylene with no catalyst
hydrohalonation- hydrohalogen such as HCl react with no catalyst
Hydration- production of ethanol where ethylene reacts with water in dilute sulfuric acid
what is a monomer?
the simplest molecule from which a polymer is made through polymerisation
what are the common polymers made from ethylene?
polyethylene
polystyrene
polyvinylchloride
polyproplyene
how can something like polyethylene be made from ethylene?
numerous ethylene molecules join together through the breakage of their double bonds, forming a long chain of repeating monomer units
what type of polymer is polyethylene?
an addition polymer
what is an addition polymer?
an addition polymer is a polymer made from the joining of individual monomers without the loss of any atoms. in some ways it can be thought of as the reverse of cracking, where long chain saturated hydrocarbons are formed through joining countless unstaturated hydrocarbons together
what are the two types of polyethylene?
HDPE and LDPE
high and low density polyethylene
what are the conditions like underwhich LDPE is made?
- temp range of 80-300 degrees celcius
- very high pressures (3000 atms)
what are the three steps in the production of LDPE
Initiation
Propagation
Termination
what occurs in the initiation stage for LDPE?
- oxygen or organic peroxide initiates the rxn
- produces ethylene free radicals which are denoted by R.
what occurs in the propagation stage for LDPE?
-chain grows via the joining of more monomer units
what occurs in the termination stage for LDPE?
-chain growth eventually stops, comes into contact with another free radical
what are the properties of LDPE?
- extensive branching and is widely spaced apart
- weak dispersion forces present due to wideness
- low MP and BP
- extensive branching is a cause for its low density
what are some uses of LDPE?
disposable plastic bags
plastic trays
cling wrap
plastic takeaway boxes
why is it important to seek alternative sources of compounds presently obtained from the petrochemical industry?
- petrochemicals are non renewable; as societies become more industralised the need for petrochemicals will become so great that every source runs out completely
- current production trends for petrochemicals are unsustainable
- current sourced petrochemicals are non biodegrabale, and thus build up and lead to major disposal problems and mass strain on landfills
- current petrol products burn uncleanly, releasing harmful pollutants into the atmosphere such as carbon dioxide and sulfur dioxide. contributes to the greenhouse effect and acid rain.
what is a condensation polymer?
a polymer chain formed by the joining of monomer units whcih detach and condense out small molecules, unlocking the monomers to be attached.
usually this released molecule is water
what is cellulose?
cellulose is a condensation polymer made from glucose monomers. it is a major component of plant cell walls and a major component of biomass
what is biomass?
biological material derived from livng or recently living organisms
what are some advantages in using cellulose as a raw material to build petrochemicals?
- its abundant and readily available from plant waste material
- its renewable and reduces the greenhouse effect when grown
- more biodegrable than petrochemical plastics, and so can be broken down much easier and thus wont take up much space
what are the disadvantages in using cellulose as a raw material to build petrochemicals?
- good for short terms plastics but not long terms once due to its biodegradability
- immense amount of energy required to convert cellulose into glucose; not ecomonmically viable, also becomes non environmentally friendly as fuels are burned and used up to extract them anyway
how do i turn ethene into ethanol?
react it with water in the addition reaction in conjunction with dilute sulfuric acid as a catalyst
how do i turn ethanol into ethylene?
place the ethanol into a concentrated solution of hydrogen sulphate, and warla
what is a galvanic cell?
a galvanic cell is a device which converts chemical energy into electrical energy
what does a galvanic cell consist of?
a galvanic cell consists of:
- two electrodes, one anode and one cathode
- two electrolyte solutions
- one salt bridge
- two containers or beakers
what does a salt bridge do in a galvanic cell?
a salt bridge allows the migration of ions to maintain a balance of negative and positive charges in each half cell.
anions migrate to the anode and cations migrate to the cathode
what is the salt bridge(what is it made of)?
usually an ionic substance like potassium nitrate
what happens at the anode in a galvanic cell?
there is a loss of electrons at the anode, through which it is called the reductant. the more reactive substance is the one which loses electrons
what happens at the cathode in a galvanic cell?
the electrons lossed at the anode migrate to the cathode of which there is a gain of electrons. the cathode is called the oxidant. the less reactive substance is the one which gains electrons
what is a redox reaction?
a redox reaction involves the loss and gaining of electrons. reduction and oxidation reactions
OILRIG?
Oxidation is Loss, Reduction is Gain(of electrons)
AnOX RedCAT?
oxidation occurs at the anode, and reduction happens at the cathode.
what is an electrode?
a conductive material that is connected to the external circuit in a galvanic cell
what is an electrolyte?
a substance, either a solution or a solid in a molten state, which accomodates the flow of electrons and hence conducts electricity.
what is an isotope?
an isotope is an element that has the same number of protons but a different number of neutrons.
what are the conditions required for an element to be radioactive?
an element with an atomic number <20 must:
not have a proton:neutron ratio of 1:1
an element with an atomic number 20
what are the three types of radiation?
alpha, beta and gamma radiation
what is alpha radiation and what is its charge?
positively charged helium nucleus with +2 charge
what is beta radiation and what is its charge?
negatively charged electron with -1 charge
what is gamma radiation what is its charge?
high energy photon with no charge (0)