Iron And Aluminium Extraction Flashcards
How is the method of extraction of iron related to its position in the reactivity series?
Iron is below carbon, so is extracted by heating with carbon in a blast furnace - ‘displacement’ reaction.
How is the method of extraction of aluminium related to its position in the reactivity series?
Aluminium is above carbon, so is extracted by electrolysis.
How is aluminium extracted from purified aluminium oxide by electrolysis?
Electrolysis is using electricity to split or separate metals.
• Aluminium oxide is dissolved in molten cryolite (an aluminium compound with a lower melting point than aluminium oxide) to lower the melting point and reduce some of the energy costs involved in extracting aluminium.
• There is a negative electrode (cathode) and a positive electrode (anode) both made from carbon.
• Aluminium metal forms at the cathode and sinks to the bottom of the tank where it is tapped off.
• Oxygen forms at the anodes and reacts with the carbon of the anodes, forming carbon dioxide and they gradually burn away.
• The positive electrodes have to be replaced frequently - adding to the cost.
What are the ionic half-equations for the reactions at the electrodes in aluminium extraction?
• At the cathode (-) :
Al³⁺ + 3e⁻ -> Al
Aluminium ions gain 3 electrons to form atoms of aluminium metal.
• At the anode (+) :
2 O²⁻ - 4e⁻ -> O₂
Two oxide ions lose 4 electrons to form an oxygen molecule.
What happens in the blast furnace?
- Haematite (iron ore), limestone and coke (carbon) are fed into the blast furnace.
- Hot air is blasted in at the bottom of the blast furnace.
- The carbon reacts with oxygen from the air to form carbon dioxide.
- The carbon dioxide reacts with more carbon to form carbon monoxide.
- Carbon monoxide reduces iron oxide to iron. The molten iron is tapped off at the very bottom.
- Molten slag (waste) is tapped off at an opening just above the very bottom.
What are the uses of iron?
Iron is used to make cars and bridges because it is hard, and has a high tensile strength (resists being stretched).
What are the uses of aluminium?
Aluminium has a very thin layer of its oxides on the surface, that stops air and water getting to the metal and corroding it - making it very useful.
• Aluminium is used for aircrafts, trains, overhead power canes, saucepans and cooking foil.
What is the reactivity series?
Peter sold little cats making all zebras increase cub size greatly • potassium • sodium • lithium • calcium • magnesium • aluminium • zinc • iron • copper • silver • gold
This reaction occurs in the blast furnace:
C + O₂ -> CO₂
What is the raw material in this reaction that reacts with the oxygen and why is it important in the blast furnace?
Coke is the raw material, which is important because it produces heat.
What are two uses of carbon dioxide, and what properties do these uses depend on?
- Carbonating drinks - must be soluble in water.
* Fire extinguishers - must be denser than air so does not allow burning (combustion).
What is the purpose of oxygen in the extraction of iron?
- Produce heat / maintain the temperature of the furnace.
* Form the reducing agent.
What is the common name for calcium silicate?
Slag.
What is the common name for calcium oxide?
Quicklime.
Which reaction in the blast furnace is used to produce heat?
Carbon and oxygen to make carbon dioxide - C + O₂ -> CO₂.
Which reaction in the blast furnace is a neutralisation reaction?
Calcium oxide reacting with sand (silicon dioxide) to make calcium silicate (slag) - CaO + SiO₂ -> CaSiO₃.
