Question

(b) Aluminium is obtained from alumina state
(i) Electrolyte used
(ii) Write cathode reaction
(iii) Why anode is replaced​

Answer 1

Answer:

b Aluminium ore is called bauxite (Al 2O 3). The bauxite is purified to yield a white powder – aluminium oxide (also known as alumina) – from which aluminium can be extracted. The extraction is done by electrolysis , but first the aluminium oxide must be melted so that electricity can pass through it.

Explanation:

i.Electrolytes are chemical compounds such as liquids or gels that contain ions and can conduct electricity when molten or dissolved in a solution. Electrolytes are necessary for batteries to function and for cells to regulate their electrical charge and the flow of water molecules across cell membranes.

ii. The cathode is where reduction takes place and electrons are gained. ... The half-reaction on the anode, where oxidation occurs, is Zn(s) = Zn2+ (aq) + (2e-). The zinc loses two electrons to form Zn2+. The half-reaction on the cathode where reduction occurs is Cu2+ (aq) + 2e- = Cu(s).

iii.

(1) During electrolysis of alumina, the oxygen liberated at the carbon anode reacts with graphite rods (carbon anode) and forms carbon dioxide. (2) As the anodes gets oxidised during electrolysis of alumina, they are continuously eroded. Hence, it is necessary to replace anodes from time to time.

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