U2 T6 Redox, Rusting, Iron Flashcards
What is a redox reaction?
A reaction in which oxidation and reduction occur at the same time
What is an oxidation reaction?
It is the gain of oxygen, loss of hydrogen or loss of electrons
What is reduction?
It is the loss of oxygen, gain of hydrogen or gain of electrons
What is the equation for the extraction of iron in the blast furnace?
Iron(iii) oxide + carbon monoxide -> iron + carbon dioxide
Fe2O3(s) + 3CO(g) -> 2Fe(l) + 3CO2
What is the equation for the rusting of iron?
Iron + oxygen + water -> hydrated iron(iii) oxide
4Fe + 3O2 + 2xH20 -> 2Fe2O3-.xH2O
What is the equation for the extraction of aluminium by electrolysis?
2Al2O3(s) -> 4Al(l) + 3O2(g)
What is the equation for the reduction of ammonia in the Haber process?
N2(g) + 3H2(g) 2NH3(g)
What is rust?
Rust is hydrated iron (iii) oxide
What 5 ways can we prevent rusting?
1) barrier methods eg painting
2) oil
3) sacrificial protection eg magnesium bolted to bottom of boat
4) alloying
5) galvanising
What is galvanising?
It is a process which bonds a layer of zinc metal onto the surface of steel. The zinc reacts with the air to form zinc oxide, giving a protective layer. Even if it is scratched, it protects the steel because it is more reactive.
What is another name for galvanising?
Sacrificial Protection. A more reactive metal will react before a less reactive
What is haematite?
Iron ore
What happens in a blast furnace?
Iron is extracted from iron oxide Fe2O3 (haematite) by reduction
What are the three stages in the blast furnace?
1) formation of reducing agent (carbon monoxide)
2) reduction of iron oxide to iron
3) removal of the impurity
What happens in stage 1 in the blast furnace?
Hot air is blown in at the base of the furnace and coke burns to heat the furnace to 1500° forming carbon dioxide
C + O -> CO2
The carbon dioxide reacts with more carbon to create carbon monoxide
CO2 + C -> 2CO
What happens at stage 2 in the blast furnace?
The carbon monoxide reduces the iron oxide to iron.
Fe2O3 + 3CO2 -> 2Fe + 3CO2
What happens at stage 3 in the blast furnace?
The main impurity is sand. Limestone is added which thermally decomposes to calcium oxide.
CaCO3 -> CO2 + CaO
Calcium oxide combines with sandy impurities (silicon dioxide) to form slag (calcium silicate)
CaO + SiO2 -> CaSiO3
What is slag?
Calcium silicate
What is slag used for?
Used to make roads, landfill, and foundations for buildings
How are the waste gases used?
They are used to heat up the furnace, reducing energy costs
What is the main impurity in crude iron?
Carbon
How is crude iron made into steel?
The carbon content is reduced
Why is steel stronger than iron?
Other atoms interrupt the regular arrangement of the iron, meaning it is stronger as it is harder for the layers to slide over each other
How is steel used?
1) used to make frames of large buildings and bridges
2) used in cables because it is strong under tension
3) used to reinforce concrete because it expands and contracts st the same rate when bested and cooled and adds strength and flexibility to the concrete
