2.2 Redox, Rusting And Iron

Question 1

What is sacrificial protection and how does it work ?

Answer 1

• Ships hulls and marine oil rigs are made of steel but are used in an environment where rust is going to be a serious problem
• Sacrificial protection involves the use of another metal that reacts before iron does
• The more reactive metal (zinc or magnesium) reacts with oxygen first - so it is sacrificed to protect the iron from rusting
• The zinc or magnesium blocks can easily be replaced when they have corroded away over time
• In oil rigs and ship hulls bars or blocks are attached to the hulls or supporting rig legs to reduce rust formation

Question 2

Why is aluminium not suitable for use in Sacrificial protection?

Answer 2

Even though Aluminium is higher than iron in the reactivity series it’s not suitable for use in Sacrificial protection as aluminium does not actually corrode faster than iron because a thin layer of aluminium oxide forms on the surface and so prevents further oxidation

Question 3

What is a redox reaction?

Answer 3

A redox reaction is a reaction in which both oxidation and reduction occur

Question 4

What is oxidation in terms of oxygen?

Answer 4

Oxidation is the gain of oxygen

Question 5

What is oxidation in terms of oxygen?

Answer 5

Oxidation is the gain of oxygen

Question 6

What is oxidation in terms of hydrogen?

Answer 6

Oxidation is the loss of hydrogen

Question 7

What is oxidation in terms of electrons?

Answer 7

Oxidation is the loss of electrons

Question 8

What is reduction in terms of oxygen?

Answer 8

Reduction is the loss of oxygen

Question 9

What is reduction in terms of hydrogen?

Answer 9

Reduction is the gain of hydrogen

Question 10

What is reduction in terms of electrons?

Answer 10

Reduction is the gain of electrons

Question 11

Name the 3 substances which are present in the charge added to the blast furnace?

Answer 11

• Coke (Mainly Carbon)
• Limestone ( Calcium Carbonate)
• Iron ore ( Haematite)

Question 12

What are the three main processes in the extraction of iron n the Blast furnace

Answer 12

1) The formation of Carbon monoxide (the reducing agent)
2) The reduction of Haematite (Iron (III) oxide ) to iron
3) The removal of acidic impurities

Question 13

What is the first process in the extraction of iron in th blast furnace?

Answer 13

• The formation of Carbon monoxide (the reducing agent)
• The Coke (mainly carbon) burns in the presence of hot air to form carbon dioxide, which further reacts with more coke to produce carbon monoxide gas, which is the reducing agent
• Carbon + oxygen > Carbon dioxide
  C + O > CO²
• Carbon Dioxide + carbon > Carbon monoxide
  CO² + C > 2CO

Question 14

What is the second process in the extraction of iron in the blast furnace?

Answer 14

• The reduction of Haematite (iron(III)oxide) to iron
• The carbon monoxide reacts with the Haematite Iron(III) oxide because carbon is more reactive than iron.
• It takes the Oxygen from the iron
• Because the temperature of the furnace is very high, the iron is in kolten form and therefore sinks to the bottom where it can be tapped off
• carbon monoxide + Iron(III)oxide > carbon dioxide + iron
• 3CO + Fe²O³ > CO² + 2 Fe

Question 15

What is the third and final process of the extraction of iron in the blast furnace?

Answer 15

• The removal of acidic impurities
• The limestone is there to remove acidic impurities like silicon dioxide ( sand)
• At the high temperature within the furnace, the limestone thermally decomposes to form calcium oxide and carbon dioxide
• Calcium Carbonate > Calcium Oxide + Carbon Dioxide
• CaCO³ > CaO + CO²
• The calcium oxide formed then goes onto react with silicon dioxide to form calcium silicate otherwise referred to as “slag”, the waste material “slag” is less dense than iron so it floats on the molten iron and it is removed and allowed to cool before being sold on for uses such as road building.
• Calcium oxide + silicon dioxide > Calcium Silicate
• CaO + SiO² > CaSiO³