C6.3 - The Extaction Of Aluminium (Finished) Flashcards
Why is carbon not used in the extraction of aluminium?
It is not reactive enough to displace the aluminium from its compounds
What compound is electrolysed to get aluminium?
Aluminium oxide
What is aluminium ore called?
Bauxite
What do you have to do with bauxite to get aluminium oxide?
Separate the aluminium oxide from the ore
Why does the electrolysis of aluminium oxide take lots of energy?
Becuase aluminium oxide has to be melted to free the ions but it has a melting point of 2050 °C
How do chemists save some of the energy when electrolysing aluminium oxide?
By mixing the aluminium oxide with molten cryolite, the mixture will electrolyse at 850 °C
What does aluminium oxide form when electrolysed?
Aluminium and Oxygen
Where is the aluminium and oxygen formed in electrolysis of Al2O3?
Aluminium at the cathode, Oxygen at the anode
What electrode is used in making aluminium?
Carbon
Why do carbon anodes in electrolysis of aluminium oxide need to be replaced?
The oxygen produced reacts with the hot carbon anodes making CO2
What is the half equation at the cathode for Al2O3 electrolysis?
Al^3+ + 3e^- -> Al
What charge do the ions of Al2O3 have?
Al has 3+
O has 2-
What is the half - equation at the anode in Al2O3 electrolysis?
2O^2- -> O2 + 4e^-
Describe what happens to the Al3+ ions in the electrolysis of aluminium oxide?
The positive Al3+ ions are attracted to the negative electrode where they pick up three electrons and turn into neutral aluminium ions.
Describe what happens to the O2- ions in the electrolysis of aluminium oxide?
The O2- ions are attracted to the positive electrode where they loose two electrons to turn to neutral oxygen atoms. They combine to form O2 molecules
