ICSE Class 10 Chemistry
Question 12 of 18
Solved 2019 Question Paper ICSE Class 10 Chemistry — Question 11
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Question Answer the following questions based on the extraction of aluminium from alumina by Hall-Heroult's Process.:
(i) What is the function of cryolite used along with alumina as the electrolyte?
(ii) Why is powdered coke sprinkled on top of the electrolyte?
(iii) Name the electrode, from which aluminium is collected.
(i) Addition of cryolite —
- lowers the fusion point of the mixture i.e., mixture fuses around 950°C instead of 2050°C.
- enhances the mobility of the fused mixture by acting as a solvent for the electrolytic mixture.
- enhances the conductivity of the mixture since, pure alumina is almost a non-conductor of electricity.
(ii) The layer of powdered coke is sprinkled over the electrolytic mixture as :
- it prevents burning of carbon electrodes in air at the emergence point from the bath.
- it minimizes or prevents heat loss by radiation.
(iii) Cathode