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ICSE Class 10 Chemistry Question 18 of 19

Solved 2017 Question Paper ICSE Class 10 Chemistry — Question 18

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Question

Question 7(b)

Answer the following questions with respect to the electrolytic process in the extraction of aluminum:

(i) Identify the components of the electrolyte other than pure alumina and the role played by each.

(ii) Explain why powdered coke is sprinkled over the electrolytic mixture.

Answer

(i) Cryolite and fluorspar are components of the electrolyte. Addition of cryolite enhances the conductivity of the mixture since, pure alumina is almost a non-conductor of electricity. Addition of both cryolite & fluorspar lowers the fusion point of the mixture i.e., mixture fuses around 950°C instead of 2050°C.

(ii) The layer of powdered coke is sprinkled over the electrolytic mixture as :

  1. it prevents burning of carbon electrodes in air at the emergence point from the bath.
  2. it minimizes or prevents heat loss by radiation.