Chemistry In Industry (Metals, Iron, Aluminium) Flashcards
Most metals are found in _______
Ores
Metals often have to be separated from their ________
Oxides
Metals above carbon in the reactivity series are extracted by what method
Electrolysis
Metals below carbon in the reactivity series are extracted by what method
Heating with carbon monoxide
What is used in the electrolysis of aluminium
Molten cryolite
Why is molten cryolite used in the electrolysis of aluminium
The aluminium oxide dissolves in it and brings the temperature down to about 900C
Aluminium is extracted from aluminium oxide. Why does molten aluminium oxide conduct electricity
Because it has free ions
Electrolysis of aluminium oxide:
Positive Al3+ ions are attracted to the negative electrode (________)
The negative O2- ions are attracted to the positive electrode (________)
Cathode
Anode
Why does the positive anode often need repacing
By getting worn down by the oxygen
Half equation of aluminium oxide a the cathode:
Al3+ + 3e- –> Al
Half equation of aluminium oxide at the anode:
2O2- –> O2 + 4e-
Complete equation for the decomposition of aluminium oxide
Aluminium oxide –> Aluminium + Oxygen
Why is electrolysis expensive
Lots of electricity used
Replacement of positive electrodes (anode) needed
What are the raw materials in the extraction of iron
Iron ore
Coke
Limestone
What is coke and what does it do
Almost pure carbon (reduces the iron oxide to iron metal)
What does limestone do
Limestone takes away impurities in the form of slag
What is the first step in the reduction of iron ore to iron
Hot air is blasted in, making the coke burn faster than usual. This raises the temperature to about 1500C
The coke burns and produces Carbon dioxide.
What is the equation for this
C + O2 –> CO2
Carbon + Oxygen –> Carbon dioxide
The Co2 then reacts with the unburnt coke form CO.
What is the equation for this
CO2 + C –> 2CO
Carbon dioxide + Carbon –> Carbon monoxide
The carbon monoxide then reduces the iron ore to iron.
What is the equation for this
3CO + Fe2O3 –> 3CO2 + 2Fe
Carbon monoxide + Iron (|||) oxide –> Carbon dioxide + Iron
What is the main impurity in the blast furnace
Sand (Silicon dioxide)
What removes the silicon dioxide
Limestone
The limestone is decomposed by the heat into calcium oxide and CO2.
What is the equation for this
CaCO3 –> CaO + CO2
The calcium oxide then reacts with the sand to form calcium silicate (slag), which is molten and can be tapped off.
What is the equation for this
CaO + SiO2 —> CaSio3 (molten slag)
What can cooled slag be used for?
Road building
Fertiliser
Describe how iron is produced from iron ore coke in the blast furnace
The coke burns (with oxygen) to produces CO2
The Co2 reacts with the unburnt coke to form CO
The CO reduces the iron ore to iron (+ CO2)
Properties of both iron and aluminium:
They both: Are dense Are good conductors of heat and electricity Are malleable Are strong Have high melting points
What is wrought iron and what are its uses
Pure iron
Gates, railing
You can mix iron with other elements to make _______
Alloys
Stainless steel is an alloy of iron. What can it be used for
Cutlery, cooking pans
What is the main problem with iron
It rusts
What is aluminium used for
Aeroplanes
Drink Cans
What makes aluminium more suited for aeroplanes than iron
It doesn’t corrode
It is lighter (less dense)
