U2 T6 Redox, Rusting, Iron

Question 1

What is a redox reaction?

Answer 1

A reaction in which oxidation and reduction occur at the same time

Question 2

What is an oxidation reaction?

Answer 2

It is the gain of oxygen, loss of hydrogen or loss of electrons

Question 3

What is reduction?

Answer 3

It is the loss of oxygen, gain of hydrogen or gain of electrons

Question 4

What is the equation for the extraction of iron in the blast furnace?

Answer 4

Iron(iii) oxide + carbon monoxide -> iron + carbon dioxide

Fe2O3(s) + 3CO(g) -> 2Fe(l) + 3CO2

Question 5

What is the equation for the rusting of iron?

Answer 5

Iron + oxygen + water -> hydrated iron(iii) oxide

4Fe + 3O2 + 2xH20 -> 2Fe2O3-.xH2O

Question 6

What is the equation for the extraction of aluminium by electrolysis?

Answer 6

2Al2O3(s) -> 4Al(l) + 3O2(g)

Question 7

What is the equation for the reduction of ammonia in the Haber process?

Answer 7

N2(g) + 3H2(g) 2NH3(g)

Question 8

What is rust?

Answer 8

Rust is hydrated iron (iii) oxide

Question 9

What 5 ways can we prevent rusting?

Answer 9

1) barrier methods eg painting
2) oil
3) sacrificial protection eg magnesium bolted to bottom of boat
4) alloying
5) galvanising

Question 10

What is galvanising?

Answer 10

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.

Question 11

What is another name for galvanising?

Answer 11

Sacrificial Protection. A more reactive metal will react before a less reactive

Question 12

What is haematite?

Answer 12

Iron ore

Question 13

What happens in a blast furnace?

Answer 13

Iron is extracted from iron oxide Fe2O3 (haematite) by reduction

Question 14

What are the three stages in the blast furnace?

Answer 14

1) formation of reducing agent (carbon monoxide)
2) reduction of iron oxide to iron
3) removal of the impurity

Question 15

What happens in stage 1 in the blast furnace?

Answer 15

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

Question 16

What happens at stage 2 in the blast furnace?

Answer 16

The carbon monoxide reduces the iron oxide to iron.

Fe2O3 + 3CO2 -> 2Fe + 3CO2

Question 17

What happens at stage 3 in the blast furnace?

Answer 17

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

Question 18

What is slag?

Answer 18

Calcium silicate

Question 19

What is slag used for?

Answer 19

Used to make roads, landfill, and foundations for buildings

Question 20

How are the waste gases used?

Answer 20

They are used to heat up the furnace, reducing energy costs

Question 21

What is the main impurity in crude iron?

Answer 21

Carbon

Question 22

How is crude iron made into steel?

Answer 22

The carbon content is reduced

Question 23

Why is steel stronger than iron?

Answer 23

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

Question 24

How is steel used?

Answer 24

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