Extraction of Metals Flashcards
how do you extract aluminium?
electrolysis
how do you extract iron or copper?
reduction
what is O.I.L.R.I.G.?
Oxidation
Is
Loss
Reduction
Is
Gain
oxidation can be…
- loss of electrons
- addition of oxygen
- loss of hydrogen
reduction can be…
- gain of electrons
- loss of oxygen
- gain of hydrogen
why is the extraction of iron a reduction reaction? what is the reducing agent?
Fe2O3 + 3CO —> 2Fe + 3CO2
Fe2O3 has lost oxygen
CO is the reducing agent
… reative atoms … … reactive atoms
more reative atoms displace less reactive atoms
what is a metal ore?
a mineral or mixture of minerals from which it is ‘economically viable’ to extract some metal
ore = rock containing metal
what is economically viable?
enough metal in ore to sell a metal or more than it cost to extract
what is rust?
hydrated iron oxide
what to most ores contain?
metal oxides
what do you need to do to extract a metal from a metal oxide?
reduce the oxygen (reduction reaction)
what two factors must you consider when deciding on the method of extraction?
cost of energy
cost of reducing agent
what is REDOX
it is both reduction and oxidation
they occur together in REDOX
what is a reducing agent?
a substance that reduced something else (removes oxygen from another substance)
what is an oxidising agent?
a substance that oxidises something else (gives oxygen to another substance)
what is the order of the reactivity series from most reactive to least reactive?
potassium
sodium
calcium
magnesium
aluminium
carbon
zinc
iron
tin
lead
hydrogen
copper
silver
gold
platinum
how do you remember the order of the reactivity series from most reactive to least reactive?
polly
smith
cut
my
amazingly
cool
zebra
into
two
lamp
hamburger
chops
creating
super
gravy
platas
what are the raw materials in the blast furnace?
coke (carbon)
haematite (ore iron oxide)
limestone (mainly calcium carbonate)
air (oxygen)
what are the reactions in the blast furnace?
carbon + oxygen —> carbon dioxide
carbon dioxide + carbon —> carbo monoxide
carbon monoxide + iron oxide —> iron + carbon dioxide
calcium carbonate —> calcium oxide + carbon dioxide
calcium oxide + silicon dioxide —> calcium silicate
what is the function of the raw materials in the blast furnace?
iron ore (haematite): a compound that contains iron
coke: burns in air to produce heat, and reacts to form carbon monoxide (needed to reduce the iron oxide)
limestone: helps to remove acidic impurities from the iron by reacting with them to form molten slag
air: allows the coke to burn, and so produces heat and carbon monoxide
balance the equation for carbon + oxygen —> carbon dioxide
carbon + oxygen —> carbon monoxide
C + O2 —> CO2
balance the equation for carbon dioxide + carbon —> carbon monoxide
carbon dioxide + carbon —> carbon monoxide
CO2 + C —> 2CO
balance the equation for carbon monoxide + iron oxide —> iron + carbon dioxide
carbon monoxide + iron oxide —> iron + carbon dioxide
3CO + Fe2O3 —> 2Fe + 3CO2
balance the equation for calcium carbonate —> calcium oxide + carbon dioxide
calcium carbonate —> calcium oxide + carbon dioxide
CaCO3 —> CaO + CO2
limetsone decomposes to form calcium oxide and release carbon dioxide gas
balance the equation for calcium oxide + silicon dioxide —> calcium silicate
calcium oxide —> silicon dioxide + calcium silicate
CaO + SiO2 —> CaSiO3
calcium oxide reacts with silica impurities to form calcium silicate (a.k.a. slag)
label this diagram
which reeaction takes place in zone 1?
carbon + oxygen —> carbon dioxide
which reeaction takes place in zone 2?
carbon dioxide + carbon —> carbon monoxide
which reeaction takes place in zone 3?
carbon monoxide + iron oxide —> iron + carbon dioxide
why does slag float on top of iron?
slag is less dense
iron is more dense so it sinks
what is slag and how does it form in the Blast furnace?
slag is moletn waste and is formed when calcium oxide and silicon dioxide react together
what can slag be used for?
sement and making roads
what does a metal lose when it reacts with oxygen?
it loses its lustre (shiny surface)
it has tarnished
what is the general formula for when a metal reacts with oxygen?
metal + oxygen —> metal oxide
what is formed when a metal reacts with acid?
hydrogen gas and a salt are always formed
explain the reaction with aluminium and acid
aluminium forms a layer of oxide extremely quickly when exposed to air
this prevents the acid from reacting with the aluminium as quickly as it should
what is the general formula for when a metal reacts with acid?
metal + acid —> metal salt + hydrogen
why do some metals, like magnesium, not react in cold water?
there is not enough energy
it will react in hot water because the heat provides extra energy
how do you test for hydrogen?
put a lit splint in a test tube
if a squeky popping sound was heard then hydrogen is presented
what is the general formula for when a metal reacts with water?
metal + water —> metal hydroxide + hydrogen
complete this recativity table
what can molten iron be used for
it can be pured onto crack and fractures on railway links to join them
what are the properties of aluminium
low density
good electrical conductor
resistant to corrosion
easy to shape
strong when alloyed with other metals
non-magnetic
good thermal conductor
why does aluminium have a low density?
atoms are not packed closely together
iron has a higher density
why is aluminium very reactive?
reacts extremely quickly
forms aluminium oxide which prevents further reaction
does not corrode
why is aluminium alloyed?
to become stronger
pure aluminium is soft
impurities mean aluminium atoms cannoyt slide easily over each other
what is electrolysis?
using electricity to split or seperate atoms
used to extract highly reactive metals
an anode is positive/negative
positive
a cathode is positive/negative
negative
negative ions move to which electrode?
positive anode electrode
positive ions move to which electrode?
negative cathode electrode
negative ions … electrons at the … electrode to become … - this is …
negative ions lose electrons at the positive electrode to become neutral - this is oxidation
positive ions … electrons at the … electrode to become … - this is …
positive ions gain electrons at the negative electrode to become neutral - this is reduction
from where is aluminium extracted?
its ore
what is the definition of electrolysis?
the process by which ionic substances are decomposed (broken down) into simpler substances when an electric current is passed through them
the substance that is broken down is called the electrolyte
what are the native metals in the reactivity series?
copper
silver
gold
platinum
how are native metals extracted?
they won’t need to be extracted becuase they are so unreactive they are found on their own, not in a metal oxide
what are the metals above carbon in the reactivity series?
potassium
sodium
calcium
magnesium
aluminium
how are the metals above carbon in the reactivity series extracted?
electrolysis
they have more reactive than carbon and thus carbon cannot displace them
what are the metals below carbon in the reactivity series?
zinc
iron
tin
lead
copper
how are the metals below carbon in the reactivity series extracted
reduction
usually by heating them with carbon in the blast furnace (displacement recaction)
in electolysis, what moves to the cathcode?
Al3+
what reaction happens at the cathode?
Al3+ + 3 electrons- —> Al(s)
this is reduction
what reaction happens at the anode?
O2- —> 0.5 O2 + 2 electrons-
this is oxidation
what are the electrodes in electroylis made of
graphite
why are electrodes made of graphite?
graphite is a good conductor of electricity
why must the electrodes be replaced regularly?
oxygen produced burns the carbon electrode away (combustion)
is electrolysis expensive or cheap and why?
expensive
electricty to burn fossil fuels
graphit is expensive
what is cyrolite and why is it used?
it is an ore of aluminium
bauxite has a high melting point so cyrolite, with a low melting point, ismixed with bauxite so it dissolved in the cyrolite
it makes the process less expensive as it reduces some of the energy costs involved in extracting aluminium
why is electrolysis dangerous
high amounts of electricty is used
why does aluminium oxide need to be molten in electrolysis?
so the ions can move
so electrictity can pass throught it
aluminium is a very good conductor of electricity and has a low density
give one use of aluminium which relies on both of these properties
pylons
what elements can pure aluminium be alloyed to strengthen it?
silicon
copper
magnesium
why does aluminium resist corrosion?
it has a very thin, but very strong, layer of aluminium oxide on its surface
this prevents anything else getting to the surface and reacting with it
what products is aluminium useful for? whY?
because aluminium doesn’t corrode it’s useful for products that come in contact with water
e.g. drink cans - you wouldn’t want rust in your drink
aluminium is much less/more dense than iron which makes it lighter/heavier
aluminium is much less dense than iron which makes it lighter
because aluminium is less dense and therefore lighter than iron, it is useful when …
e.g. …
because aluminium is less dense and therefore lighter than iron, it is useful when the weight of the metal is important
e.g. in bicycle frames and aeroplanes
what seven properties do iron and aluminium have in common?
they are both dense
they are both lustrous (shiny)
they both have high melting points
they both have a high tensile strencgth - they’re strong and hard to break
they are both malleable - can be hammered into a different shape
they are both good conductors of electricity
they are both good conductors of heat
how is pig iron formed?
molten iron straight from the furnace that has been cooled rapidly and solidified by running it into sand moulds
how is cast iron formed?
when pig iron (molten iron straight from the furnace that has been cooled rapidly and solidified by running it into sand moulds) is remelted and cooled under controlled conditions
is cast iron pure? what percentage of carbon does it contain?
it is very impure iron, containing about 4% carbon as its main impurity
what is cast iron a mixture of?
iron, carbon and silicon
what are three properties of cast iron?
cast iron is very fluid when it is molten and doesn’t shrink much when it solidifies (this makes it ideal for making castings)
it is very hard
it is very brittle, tending to shatter if it is hit hard
what are five uses of cast iron?
making castings
manhole covers
guttering
drainpipes
cylinder blocks in car engines
what percentage of carbon does mild steel contain? what does this increase?
0.25%
this small amount of carbon increases the hardness and strength of the iron
what are six uses of mild steel?
wire
nails
car bodies
ship building
girders (for construction)
bridges
what is pure iron known as?
wrought iron
what did wrought iron used to be for?
to make decorative gates and railings, but has now been largely replaced by mild steel
explain the properties of wrought iron
the purity of wrought iron makes it very easy to work because it is fairly soft
the softness and lack of strength mean that it isn’t useful for structural purposes
what percentage of carbon does high-carbon steel contain? what does increasing the carbon content do to the iron?
up to 1.5% carbon
increasing the carbon content makes the iron harder, but at the same time it gets more britt;e
what are two uses of high-carbon steel?
cutting tools
masonry nails - designed to be hammered into concrete blcoks or brickwork where a mild steel nail would bend
if you miss a masonry nail, it tends to break into two bits because of its increased brittleness
what is stainless steel?
an alloy of iron with chromium and nickel
in stainless steel, what is the use of the chromium and nickel?
chromium and nickel form strong oxide layers, and these layers protect the iron
is stainless steel resistant to corrosion? why?
stainless steel is very resistant to corrosion because the chromium and nickel form strong oxide layers that protect the iron
what are six uses of stainless steel?
kitchen sinks
saucepans
knives
forks
gardening toolds
major uses for it in the brewing, dairy and chemical industries, where corrosion-resistant vessels are essential
when does iron rust? how does this process work?
in the presence of oxygen and water
iron loses electrons to form iron (II) ions, Fe2+, which are then oxidised by the air to form iron (III) oxide, Fe3+
reactions involving the water produce the actual rust
what accelerates rusting of iron?
when iron is in the presence of electrolytes such as salt
What does rusting refer to?
many metals corrode, but it is only the corrosion of iron that is referred to as rusting
What is trust and what is the formula of rust?
rust is a micture of iron (III) oxide and water
Fe2O3・xH2O where x is a number
what three ways can you prevent rusting?
by using barriers
by alloying the iron
by using sacrificial metals
how does preventing rusting by using barriers work?
by painting, coating it in oil or greese, or covering it in plastic to keep the water and and oxygen away from it
but once the coating is broken, the iron will rust
coating the iron with a metal below it in the reactivity series is just a barrier method
what is an example of preventing rust by alloying the iron?
e.g. stainless steel
even if the surface is scratched, the stainless steel won’t rust
unfortunately, stainless steel is expensive
how does preventing rusting by using sacrificial metals work?
Galvanised iron is iron that is coated with a layer of zinc
As long as the zinc layer is unscratched, it serves as a barrier to air and water. However, the iron still doesn’t rust, even when the surface is broken
Zinc is more reactive than iron, so it corrodes instead of iron. During the process, the zinc loses electrons to form zinc ions:
Zn (s) → Zn2+ (aq) + 2e-
Those electrons flow into the iron. Any iron atom which has lost electrons to form an ion immediately regains them. If the iron can’t form ions, it can’t rust
