S P Singh Solutions for Chapter: Metallurgy, Exercise 5: MISCELLANEOUS EXERCISE

Choose the most appropriate answer from the following list of oxides which fit the description. Each answer may be used only once :$[{\mathrm{SO}}_2, {\mathrm{SiO}}_2, {\mathrm{Al}}_2{\mathrm{O}}_3, \mathrm{MgO}, \mathrm{CO}, {\mathrm{Na}}_2\mathrm{O}]$

(i) A basic oxide.
(ii) An oxide which dissolves in water forming an acid.
(iii) An amphoteric oxide.
(iv) A covalent oxide of a metalloid.

Describe the role played by sodium hydroxide in the extraction of aluminium.

Describe the role of graphite played in the extraction of aluminium.

Name the solution used to react with Bauxite as a first step in obtaining pure aluminium oxide, in the Baeyer's process.

Write the equation for the reaction where the aluminium oxide for the electrolytic extraction of aluminium is obtained by heating aluminium hydroxide.

Name the compound added to pure alumina to lower the fusion temperature during the electrolytic reduction of alumina. (answer in one word)

Write the equation for the reaction that occurs at the cathode during the extraction of aluminium by electrolysis.

Explain why it is preferable to use a number of graphite electrodes as anode instead of a single electrode, during the electrolysis of aluminium.