A1 - Extraction of Alumina and Aluminium Flashcards
What ore is Alumina extracted from?
Bauxite
What substance can be extracted from Bauxite?
Alumina
What is the name of the process used to extract alumina?
Bayer process
What is the Bayer process used for?
Extracting alumina from bauxite
Why is bauxite crushed in the Bayer process?
To increase the rate of reaction
Which step in the Bayer process increases the rate of reaction?
Crushing the bauxite
What is bauxite reacted with in the Bayer process?
NaOH
What is added to cause crystallisation during the Bayer process?
Al(OH)3
What is the formula of alumina?
Al2O3
What is the name of Al2O3?
Alumina
What ions does Al2O3 contain?
Al3+ and O2−
What is the name of the process used to extract aluminium from alumina?
Hall-Heroult electrolysis
What is the Hall-Heroult electrolysis used for?
Extracting aluminium from alumina
What is alumina dissolved in during electrolysis?
Molten cryolite
What is molten cryolite used for in the electrolysis of alumina?
Dissolving the alumina
Why is alumina dissolved instead of melted during electrolysis?
Alumina has a high melting point and it requires less energy (and is cheaper) to dissolve it
Which ions go to the positive anode in the electrolysis of alumina?
O2−
Which ions go to the negative cathode in the electrolysis of alumina?
Al3+
Write the equation for the reaction of Al3+ at the negative electrode
Al3+ + 3e− → Al
What do the Al3+ ions turn into during the electrolysis of alumina?
Molten aluminium
Why does Al form at the bottom of the electrolysis cell?
Because the aluminium that forms is molten and sinks
What is the positive anode made from in the electrolysis of alumina?
Graphite
Write the equation for the reaction of O2− at the positive electrode
2O2− → O2 + e−
What do the O2− ions turn into during the electrolysis of alumina?
O2
