Chemistry
Answer the following questions with respect to the electrolytic process – in the extraction of aluminium.
(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 :
- it prevents burning of carbon electrodes in air at the emergence point from the bath.
- it minimizes or prevents heat loss by radiation.
Related Questions
Give a reason for : Alkali metals are good reducing agents.
Name the following :
(i) An alloy of lead and tin that is used in electrical circuits.
(ii) An ore of zinc containing its sulphide.
(iii) A metal oxide that can be reduced by hydrogen.
From the list of terms given, choose the most appropriate term to match the given description:
[calcination, roasting, pulverisation, smelting] -(i) Crushing of the ore into a fine powder.
(ii) Heating of the ore in the absence of air to a high temperature.
Complete the following by selecting the correct option from the choices given –
(i) The metal whose oxide, which is amphoteric, is reduced to metal by carbon reduction …………… [Fe/Mg/Pb/Al]
(ii) The divalent metal whose oxide is reduced to metal by electrolysis of its fused salt is …………… [Al/Na/Mg/K]