Metallurgy: Bayer's and Hall's Methods for Aluminium Extraction

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What is the purpose of passing carbon dioxide gas through the warmed filtrate?

To dissolve alumina

To precipitate aluminium hydroxide (correct)

To enhance the conductivity of the solution

To increase the pH of the solution

What happens when Al(OH)3 is calcined at 1000°C?

It forms Al(OH)2

It melts into a liquid

It sublimates into a gas

It decomposes into Al2O3 and H2O (correct)

Which compound is added to the mixture during the electrolytic reduction of alumina to lower its melting point?

Calcium carbonate (CaCO3)

Sulphuric acid (H2SO4)

Cryolite (Na3AlF6) (correct)

Sodium chloride (NaCl)

What is deposited on the cathode during the electrolytic reduction of alumina?

Aluminium Signup and view all the answers

What role does graphite lining play in the steel tank during electrolysis?

It acts as the cathode Signup and view all the answers

Why do the anodes need to be changed periodically during the electrolysis of alumina?

Due to oxidation Signup and view all the answers

What are the impurities present in bauxite?

Silica, ferric oxide, titanium oxide Signup and view all the answers

Which method is used for the separation of impurities in bauxite?

Bayer's method Signup and view all the answers

What is the final product obtained after the concentrated alumina is calcined?

Aluminium oxide Signup and view all the answers

Which reagent is used to leach bauxite in Bayer's method?

Concentrated solution of caustic soda (NaOH) Signup and view all the answers

What happens to aluminium hydroxide in the Hall's process?

It forms water-soluble sodium aluminate Signup and view all the answers

What is the role of sodium carbonate in Hall's process?

To leach bauxite and form water-soluble sodium aluminate Signup and view all the answers

Metallurgy: Bayer's and Hall's Methods for Aluminium Extraction

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Questions and Answers

What is the purpose of passing carbon dioxide gas through the warmed filtrate?

What happens when Al(OH)3 is calcined at 1000°C?

Which compound is added to the mixture during the electrolytic reduction of alumina to lower its melting point?

What is deposited on the cathode during the electrolytic reduction of alumina?

What role does graphite lining play in the steel tank during electrolysis?

Why do the anodes need to be changed periodically during the electrolysis of alumina?

What are the impurities present in bauxite?

Which method is used for the separation of impurities in bauxite?

What is the final product obtained after the concentrated alumina is calcined?

Which reagent is used to leach bauxite in Bayer's method?

What happens to aluminium hydroxide in the Hall's process?

What is the role of sodium carbonate in Hall's process?

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