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5.4 Describe and explain the main reactions involved in the extraction of iron from iron ore (haematite), using coke, limestone and air in a blast furnace

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5.4 Describe and explain the main reactions involved in the extraction of iron from iron ore (haematite), using coke, limestone and air in a blast furnace

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haematite (iron ore) is mixed with limestone and calcium silicate (coke/impure carbon), then fed into the blast furnace at the top

carbon, essential reducing agent for the iron oxide, is produced in an exothermic reaction. Impure carbon burns in hot air blast to form CO2:
carbon (from limestone) + oxygen   →    carbon dioxide
C+ O2    →    CO2
the CO2 then reacts with limestone to form carbon monoxide:
carbon dioxide + carbon    →    2 carbon monoxide
CO2 + C    →    2CO

haematite is iron oxide- thus to extract iron, haematite must undergo reduction reaction to remove oxygen. carbon (from calcium silicate) is more reactive than iron, so it displaces the iron from iron oxide.

iron oxide + carbon    →    iron + carbon dioxide

2Fe2O3 + 3C    →    4Fe + 3CO2
the iron oxide is reduced to iron,

and the carbon is oxidised to carbon dioxide

In the blast furnace, the temperature is so high that carbon monoxide can be also used to reduce the iron oxide in place of carbon:

iron oxide + carbon monoxide    →    iron + carbon dioxide

Fe2O3 + 3CO    →    2Fe + 3CO2

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5.3 Write ionic half-equations for the reactions at the electrodes in aluminium extraction

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5.3 Write ionic half-equations for the reactions at the electrodes in aluminium extraction

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Positive electrode (anode):
Al(3+)(l) + 3e(-) > Al(l)
Negative electrode (cathode):
2O(2-) > 4e(-) + O2(g)

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1.49 understand why covalent compounds do not conduct electricity.

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1.49 understand why covalent compounds do not conduct electricity.

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Why? Because they do not have any free electrons or charged atoms.

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5.2 Describe and explain the extraction of aluminium from purified aluminium oxide by electrolysis, including:

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5.2 Describe and explain the extraction of aluminium from purified aluminium oxide by electrolysis, including:

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i. the use of molten cryolite as a solvent and to decrease the required operating temperature
because aluminium is very reactive, it must be extracted using electrolysis. However it is impractical to electrolyse molten aluminium oxide due to its high melting point, so it is dissolved in molten cryolite (aluminium compound with lower melting point)

ii. the need to replace the positive electrodes
Aluminium ions are attracted to the cathode & gain electrons
Oxide ions are attracted to the anode & lose electrons
> carbon anodes burn in the oxygen to form carbon dioxide

iii. the cost of the electricity as a major factor
the electrolysis cell operates at around 5-6 volts but 100,000 amps, where the heat is generated by huge currents, keeping the electrolyte molten.

diagram for (i)

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1.50 understand why ionic compounds conduct electricity only when monten or in a solution

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1.50 understand why ionic compounds conduct electricity only when monten or in a solution

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1.53 describe experiments to investigate electrolysis, using inert electrodes, of molten salts such as lead (II) bromide and predict the products 

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1.53 describe experiments to investigate electrolysis, using inert electrodes, of molten salts such as lead (II) bromide and predict the products 

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2.30 describe how reactions with water and dilute acids can be used to deduce the following order of reactivity: potassium, sodium, lithium, calcium, magnesium, zinc, iron and copper

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2.30 describe how reactions with water and dilute acids can be used to deduce the following order of reactivity: potassium, sodium, lithium, calcium, magnesium, zinc, iron and copper

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Reactions with water:
Potassium: lilac flame, potassium spits around until it is completely used up
Sodium: floats on the water, sodium is pushed around the surface of the water until it is completely used up

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2.29 understand that metals can be arranged in a reactivity series based on the reactions of the metals and their compounds: potassium, sodium, lithium, calcium, magnesium, aluminium, zinc, iron, copper, silver and gold

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2.29 understand that metals can be arranged in a reactivity series based on the reactions of the metals and their compounds: potassium, sodium, lithium, calcium, magnesium, aluminium, zinc, iron, copper, silver and gold

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1.48 understand that an electric current is a flow of electrons or ions 

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1.48 understand that an electric current is a flow of electrons or ions 

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1.52 describe experiments to distinguish between elctrolytes and non-electrolytes 

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1.52 describe experiments to distinguish between elctrolytes and non-electrolytes 

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Electrolysis is a chemical change caused by passing an electric current through a compound which is either molten or in solution

An electrolyte is a substance that undergoes electrolysis. Electrolytes all contain ions. The movement of the ions is responsible for both the conduction of electricity + the chemical changes that take place.

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5.1 explain how the methods of extraction of the metals in this section are related to their positions in the reactivity series

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5.1 explain how the methods of extraction of the metals in this section are related to their positions in the reactivity series

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Extract of reactivity series:
KPotassium
Na Sodium
Ca Calcium
Mg Magnesium
Al Aluminium
(C) Carbon
Zn Zinc
Fe Iron
Cu Copper
...

Metals including zinc and those below:
heat with carbon or carbon monoxide
can be reduced using carbon at reasonably high temperatures

Metals above zinc:
Produced by electrolysis
Metal ores given electrons directly from the cathode
> Large amounts of electricity involved > high prices