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21 Cards in this Set
- Front
- Back
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Why cant aluminium be extracted in the blast furnace?
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It is higher than carbon in the reactivity series
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What is aluminium ore known as and what is its formula?
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Alumina - Al2O3
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How do you extract Al2O3?
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Electrolysis
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What is the melting point of aluminium oxide?
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2000 degrees
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Why would aluminium oxide need to be melted to be able to extract the aluminium?
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The ions need to be free to move
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Why is 2000 degrees too high to electrolyse the aluminium oxide?
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It would melt the steel cell
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What solvent is used to dissolve Al2O3 into and what is its melting point?
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Cryolite - 1000 degrees
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What is the benefit of using cryolite?
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The operating temperature is reduced.
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What are the electrodes made out of?
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Graphite/carbon blocks
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Where are the cathodes in the cell?
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around the edges
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What happens at the cathode?
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Aluminium ions gain three electrons to become aluminium atoms
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What happens to the newly formed alumium atoms?
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They settle at the bottom due to the high temperature
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What is the half equation for the formation of aluminium atoms?
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Al3+ + 3e- -> Al
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What happens at the anode?
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The oxide ions lose two electrons forming oxygen atoms
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What is the half equation for the formation of oxygen atoms?
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2O2- -> O2 + 4e-
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What happens to the newly formed oxygen gas?
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It reacts with the carbon anodes due to the high temperatures.
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What is the equation for the anodes burning?
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C + O2 -> CO2
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What is the downside of the anodes burning?
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They need replacing monthly, increasing the cost of the process
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Why is the process so expensive?
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There is a huge amount of electricity used.
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What is a use of aluminium and why?
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low density- aeroplane bodies
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Why is there no need to paint aluminium structures?
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Aluminium oxidises in the air to form a hard coat of aluminium oxide which protects the body.
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