Section 5: Chemistry in Industry Flashcards
electrolysis is used to extract which metals?
potassium to aluminium in the reactivity series as they are more reactive than carbon
smelting is used to extract which metals?
zinc to copper in the reactivity series
how are silver, platinum and gold extracted?
mined in their pure form as they are very unreactive
describe the extraction of aluminium from purified aluminium oxide
1) bauxite (aluminium oxide) and cryolite are mined and purified
2) cryolite is heated up and bauxite is dissolved in it
3) electricity is passed through the molten mixture
4) aluminum collects at the cathode and oxygen bubbles off at the anode
why is bauxite (aluminium oxide) dissolved in cryolite before being electrolysed?
in order to lower the required operating temperature
why do the posotive electrodes used during the electrolysis of aluminium oxide have to be replaced regularly?
because oxygen reacts with the carbon anodes wearing it away
what is the largest operating cost of electrolysing aluminium oxide?
the cost of electricity
what is the reaction at the anode during the electrolysis of aluminium oxide?
2O²⁻ –> O2 + 4e-
what is the reaction at the cathode during the electrolysis of aluminium oxide?
Al³⁺ + 3e- –> Al
what are the uses of aluminium?
1) alloys in airplane construction (forms alloys with low densities)
2) electrical cables (good electrical conductor)
3) saucepans and frying pans (good thermal conductor)
4) powder in rocket fuels (combustion is very exothermic)
what are the raw materials used in the extraction of iron from iron ore?
1) Haematite (Fe2O3) - source of iron
2) Coke (C) - forms reducing agent
3) Limestone (CaCO3) - removes impurites
what are the reactions involves in the extraction of iron from iron ore?
1) C+O2 –> CO2 (supplies heat for reaction)
2) CO2 + C –> 2CO (forms reducing agent)
3) 3CO + Fe2O3 –> 3CO2 + 2Fe (produces pig iron)
what are the uses of iron?
1) gates and railings etc. (hard and resistant to rusting)
2) part of stainless steel which is used in cutlery (doesn’t rust at all)
what is crude oil?
a mixture of hydrocarbons
what are refinery gases used for?
domestic heating and cooking
what is gasoline used for?
fuel for cars (petrol)
what is kerosene used for?
fuel for aircrafts
what is diesel used for?
fuel for cars, lorries and buses
what is fuel oil used for?
fuel for ships and power stations
what is bitumen used for?
making roads and roofs
how is fractional distillation used to separate crude oil into fractions?
1) crude oil is vaporised
2) gas is passed into a fractioning column
3) fractions condense at different levels where they can be tapped off
the longer the carbon chains in fraction of crude oil the…
1) higher the boiling point
2) stronger the inter molecular forces
3) higher the viscosity
4) lower the volatility
does more branches on hydrocarbons mean stronger or weaker inter molecular forces?
weaker
order the main fractions of crude oil from lowest boiling point to highest boiling point
refinery gases gasoline kerosene diesel oil fuel oil bitumen
why is incomplete combustion dangerous?
may produce carbon monoxide which is toxic and reduces the capacity of the blood to carry oxygen
why can nitrogen oxide form in car engines?
the temperature reached is high enough to allow nitrogen and oxygen from air to react
why are nitrogen oxides and sulphur dioxides dangerous?
they react with rain water to form acid rain which:
1) damages plants as they take in the acidic water through their roots and washes minerals out of soil which the plants need.
2) some minerals that are washed into lakes kill fish
why is catalytic cracking required?
1) over supply of long chain hydrocarbons and not enough short chain hydrocarbons
2) higher demand for short chain hydrocarbons
3) alkenes can be used to make polymers/plastics
what is involved in catalytic cracking?
long-chain alkanes are converted into alkenes and shorter-chain alkanes
what are the conditions required for catalytic cracking to occur?
1) temperatures of 600-700C
2) alumina (aluminium oxide) catalyst
how are addition polymers formed?
by joining up small molecules called monomers
what is the repeat unit of poly(ethene)?
H H
C C
H H
what is the repeat unit of poly(propene)?
H H
C C
H CH3
what is poly(ethene) used for?
1) low-density poly(ethene) is used to make plastic bags
2) high-density poly(ethene) is used to make plastic bottles
what is poly(propene) used for?
used to make ropes and crates (stronger than poly(ethene))
why are addition polymers hard to dispose of?
their inertness means they do not easily biodegrade (broken down by microbes/bacteria)
what is the harber process?
a reversible reaction where ammonia is made from combining nitrogen with hydrogen
what is the source of the nitrogen used in the production of ammonia?
air
what is the source of the hydrogen used in the production of ammonia?
natural gas or the cracking of hydrocarbons
what are the conditions required in the harber process?
1) temperature of 450C
2) pressure of about 200atm
3) iron catalyst
why is the reaction mixture in the harber process cooled?
to liquifie the ammonia produced and allow the unused nitrogen and hydrogen to be recirculated
what are the uses of ammonia?
manufacture of nitric acid and fertilisers
What is meant by the term fraction?
A mixture of compounds with similar boiling points
Describe how molten slag forms in a blast furnace
1) calcium carbonate decomposes into calcium oxide
2) calcium oxide reacts with silicon dioxide
What are the reactions involved in the formation of slag?
1) CaCO3 –> CaO + CO2 (thermal decomposition)
2) CaO + SiO2 –> CaSiO3 ( neutralises acid oxide and forms slag)
Name the main ore used as the source of iron
Haematite
Name the main ore used as the source of aluminium
Bauxite
What so the role of oxygen in the extraction of iron?
1) production of heat
2) formation of reducing agent
What time of reaction is calcium oxide and sulfur dioxide?
Neutralisation
How is crude oil separate into fractions?
1) vaporise the crude oil
2) gases rise up the column
3) the fractioning column is cooler at the top
4) fractions condense when the temperature is lower than their boiling point, so they can be tapped off
What is the repeat unit of poly(chloroethene)?
H H
C C
H Cl
What is poly(chloroethene) used for?
1) drainpipes
2) electrical insulation
How is nylon formed?
Via condensation polymerisation
What does condensation polymerisation produce?
A small molecule (such as water) as well as the polymer
What are the raw materials used in the manufacture of sulfuric acid?
1) sulfur (from fossil fuels or sulfide ores)
2) oxygen (from air)
3) water
What are the conditions required in the contact process?
1) 450C
2) 2 atm
3) vanadium oxide catalyst
Describe the stages of making sulfuric acid
1) burn sulphur or heat sulfide ores strongly to produce sulphur dioxide
2) concert sulphur dioxide into sulphur trioxide using an excess of air
3) react sulphur trioxide with with concentrated sulphuric acid to give ‘oleum’ (fuming sulphuric acid)
4) react oleum with water to create concentrated sulphuric acid
What is fuming sulphuric acid called?
Oleum
What is sulphuric acid used for?
Manufacture of…
1) detergents
2) fertilisers
3) paints
What are the two reactions at the start of the contact process to form sulphur trioxide?
1) S + O2 —> SO2
2) 2SO2 + O2 —> 2SO3
What are the two reactions in the contact process to go from sulphur trioxide to sulphuric acid?
1) H2SO4 + SO3 —> H2S2O7
2) H2S2O7 + H2O —> 2H2SO4
How is sodium hydroxide and chlorine produced?
By the electrolysis is concentrated sodium chloride solution in a diaphragm cell
What is brine?
concentrated sodium chloride solution
What is the equation at the anode during the electrolysis of brine?
2Cl- —> Cl2 + 2e-
What so the equation at the cathode during the electrolysis of brine?
2H+ + 2e- —> H2
Why is a diaphragm cell used in the electrolysis of brine?
To keep the products (chlorine and sodium hydroxide) apart
What is sodium hydroxide used for?
Manufacture of…
1) bleach
2) paper
3) soap
What is chlorine used for?
1) sterilising water supplies
2) manufacturing bleach and hydrochloric acid
