Home › Maharashtra SSC (Class 10) › Chemistry › Metallurgy › During electrolytic reduction of alumina, why do…
During electrolytic reduction of alumina, why do the carbon anodes need to be replaced periodically?
AAluminium deposits on them and clogs them
BLiberated oxygen oxidises them to carbon dioxide
CMolten cryolite dissolves them into the bath
DElectric current melts them into the cathode
Answer & Solution
Correct answer: B. Liberated oxygen oxidises them to carbon dioxide
1. At the anode, oxide ions are oxidised and oxygen gas is liberated.
2. The anodes are made of carbon (graphite).
3. The hot liberated oxygen reacts with the carbon anodes to form carbon dioxide gas.
4. The anodes are thus gradually consumed and must be changed from time to time.
5. Option about aluminium clogging the anode is wrong, as aluminium deposits at the cathode.
6. Option about cryolite dissolving the anodes is wrong, as cryolite only lowers the melting point.
7. Option about current melting the anode into the cathode is wrong, as the loss is by oxidation, not melting.
_Source: Balbharati (Maharashtra Board) Class 10 Science & Technology, Ch 8 "Metallurgy", p.113_
Related questions
Metallurgy is the process of:Bronze, an alloy resistant to sun and rain, is made from which composition?An alloy in which one of the constituent metals is mercury is given which special name?In electroplating, what is coated onto a more reactive metal by electrolysis?In anodization of aluminium, the article is made the anode so that a protective layer of wDepositing a layer of molten tin on a metal surface, popularly called 'kalhaee', is known In galvanizing, why does the zinc layer corrode before the iron beneath it?In galvanizing, a thin layer of which metal is applied to protect iron or steel?