Chemistry in industry Flashcards
What’s a metal ore?
Compound with metal found in Earth which is worth extracting
Finite resource
What’s a reduction reaction?
A reaction that separates a metal from it’s oxygen
Example of a reduction reaction?
Copper oxide + Carbon = Copper + oxygen
Which elements can undergo a reduction reaction with carbon?
Anything less reactive than carbon, so the carbon can steal the oxygen
How’s a reduction reaction done?
Ore is heated with Carbon monoxide
How are compound ores with more reactive elements than carbon separated?
Electrolysis
What’s used to reduce the temperature (and costs), of the electrolysis of aluminium oxide?
Cryolite, aluminium oxide has a high boiling point, so instead it’s dissolved in cryolite, making it cheaper and easier
Why does the positive carbon electrode often need replacing?
Reacts with oxygen wears it down
What happens at the cathode at the electrolysis of Aluminium oxide?
Reduction, the aluminium gains 3 electrons
What happens at the anode at the electrolysis of Aluminium oxide?
Oxidation, oxygen loses 4 electrons
What overall reaction is the electrolysis of aluminium oxide?
Redox reaction
What’s the complete equation for the decomposition of aluminium oxide?
Aluminium Oxide = aluminium + oxygen
Why’s electrolysis expensive?
Requires a lot of electricity
Positive electrodes often need replacing
Why’s electrolysis of aluminium good?
Now it’s cheap, used to be very rare and hard to extract
How is iron extracted from haematite?
Reduction in a blast furnace
What are the raw materials put in the blast furnace?
Iron ore, containing the iron
Coke, containing carbon to reduce iron oxide to iron metal
Limestone takes away impurities in the form of slag
How does the iron ore get reduced to iron?
Hot air blasted in
Coke burns to produce carbon dioxide
Carbon dioxide reacts with unburnt coke to form carbon monoxide
Carbon monoxide reduces iron ore to iron
iron is molten at this temperature and very dense so it runs down and tapped off at the bottom
How are the impurities removed in a blast furnace?
Main impurity is silicon dioxide (sand)
Limestone decomposed by the heat to form calcium oxide and carbon dioxide
Calcium oxide reacts with silicon dioxide to form slag with is molten to tapped off
Slag can be used for road building or fertiliser
What properties do aluminium and iron have in common?
Metals Dense and shiny Conduct heat and electricity Malleable and strong High boiling points
Use of wrought iron (pure iron)?
Malleable so ornamental gates and railings
What’s an alloy?i
Irons mixed with another element, giving it different properties
What’s cast iron used for?
Hard and brittle, so cooking pans
Steel?
Hard, so car bodies
What’s the main problem with iron?
It rusts
What’s stainless steel?
Alloy of iron and chromium which doesn’t rust
Benefits of aluminium to iron?
Doesn’t corrode as layer of aluminium oxide prevents further reactions
Lighter so used in aeroplanes
What’s crude oil?
A mixture of Hydro- carbons
How is crude oil separated?
Fractional distillation
How does fractional distillation work?
Oil is heated up in a fractionating column
Longer Hydrocarbons condense earlier and drain out due to high boiling points
Shorter Hydrocarbons condense later and drain out due to lower boiling points
Features of Refinery gases?
Hydrocarbon length: 3
Uses: Bottled gas
Features of gasoline?
Hydrocarbon length: 8
Uses: fuel for vehicles
Features of Naphtha?
Hydrocarbon length: 10
Uses: Feedstock
Features of Kerosene ( Paraffin)?
Hydrocarbon length: 15
Uses: Jet engines
Features of Diesel?
Hydrocarbon length: 20
Uses: Fuel for diesel engines
Features of Fuel oil?
Hydrocarbon length: 40
Uses: Central heating
Features of Bitumen?
Hydrocarbon length: 70+
Uses: Road surfaces
What happens when fractions from crude oil are burnt as fuels?
Pollutants produced
Why is carbon monoxide poisonous?
Stops red blood cells carrying oxygen, by combining with haemoglobin
Why is sulphur dioxide produce from burning fuel?
sulphur impurities in the fuel
Why are nitrogen oxides produced?
Temperature is high enough for Nitrogen and Oxygen to react
How does Sulfur dioxide and Nitrogen oxides cause acid rain?
Reacts with clouds to form sulphuric acid, or nitric acid
Damages of Acid rain?
Makes lakes acidic
Damages limestone buildings
Features of long Hydrocarbons?
High boiling points
Features of short Hydrocarbons?
Low boiling points
What’s cracking?
Form of thermal decomposition
Why are long Hydrocarbons cracked?
The smaller ones are more useful
What does cracking also produce?
Alkenes used to make polymers
How to crack paraffin?
Heat the paraffin and make it pass over a heated catalyst in the form of alumina, Paraffin cracks, collect the alkenes
Equation for the cracking of a hydrocarbon?
Long chain alkane = shorter alkane + alkenes
What’s a monomer?
The small molecules, with carbon-carbon double bonds (alkenes)
How are addition polymers made?
When the monomers under go high pressure and a catalyst they join hands (polymerise) to form polymers
What’s a polymer?
A very long saturated chain
What does the N in a polymer equation mean?
How many repeat units there are
What’s a repeat unit?
The part of the polymer which is repeated
How do you find the monomer used to form an addition bond?
Take the repeat unit and add a double bond
What’s a condensation polymer?
When 2 monomers react and for each new bond a small molecule (eg water) is lost
Example of a condensation polymer?
Nylon, Monomer 1 + Monomer 2 = condensation polymer ( nylon) + water
Use of poly(ethene)?
Stretchable and light so bottles
Uses of Poly(propene)?
Tough/heat resistant so kettles
Uses of Poly(chloroethene)
Insulating electrical cables
Why are polymers difficult to get rid of?
Carbon carbon bonds are tough so they take a long time to bio degrade
Why can’t you burn polymers?
Release toxic gases
Best way to deal with polymers?
Reuse them
Equation for the harbour process?
Nitrogen + Hydrogen = ammonia
Use of ammonia?
Used as fertiliser
Where’s the nitrogen obtained?
Air
Where’s the hydrogen obtained?
Natural gas
What’s unique about the harbour process?
It’s reversible, so not all ammonia and hydrogen will convert into ammonia, it reaches dynamic equilibrium
What are the required conditions for the harbour process?
Pressure 200 atmospheres
Temperature 450C
Catalyst Iron
Why is the pressure so high in the harbour process?
It benefits the forward reaction, so the making of ammonia
Why is the temperature 450C
Higher temperatures favour the backwards reaction, however increasing the heat makes the reaction faster so it’s a compromise
What’s ammonium nitrate a good fertiliser?
Provides plants with Nitrogen and ammonia
What’s the contact process used for?
Making sulphuric acid
Describe the contact process?
Sulphur is burnt in air to produce sulphur dioxide
Sulphur dioxide is oxidised (with a catalyst) to form sulphur trioxide
Sulfur trioxide is dissolved in concentrated sulphuric acid to form a liquid oleum
Oleum is diluted with water to form concentrated sulphuric acid
Why’s a catalyst so important in the contact process?
A higher temperature favours the backwards reaction, but a high temperature is needed to increase the speed of the reaction
Condition for the contact process?
Temperature: 450C
Pressure 2 atmospheres
Catalyst : vanadium oxide
Uses of sulphuric acid?
Fertilisers
Detergents
Paints
What’s produced in the electrolysis of the salt brine ( sodium chloride solution)
Hydrogen chlorine and sodium hydroxide
Where’s the hydrogen gas given off?
Cathode
Where’s the chlorine gas given off??
Anode
Where is the sodium hydroxide produced?
Stays in the solution
How many electrons are gained or lost by the hydrogen and chlorine?
2
What’s chlorine used for?
Bleach or sterilisation
What’s hydrogen used for?
Harbour process, or changing oils into fats
What’s sodium hydroxide used for?
Very strong base, so soap
