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प्रश्न
Explain with reason:
In the electrolytic reduction of alumina, the graphite anode is gradually consumed.
Explain with reason:
Why the anode has to be replaced from time to time in this process?
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उत्तर
In the electrolytic reduction of alumina, the graphite (anode) is oxidised by oxygen to CO and further forms CO2, so it is consumed and has to be replaced from time to time.
\[\ce{2C + O2 -> 2CO}\]
\[\ce{2CO + O2 -> 2CO2}\]
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संबंधित प्रश्न
Name the following:
A metal oxide that can be reduced by hydrogen.
Name the compound added to pure alumina to lower the fusion temperature during the electrolytic reduction of alumina.
Give appropriate scientific reasons for Zinc oxide can be reduced to zinc metal by using
carbon, but aluminium oxide cannot be reduced by a reducing agent
Give reason for the following:
Carbon anodes are used in the electrolytic extraction of aluminium.
Give equation for the following conversion: Aluminium to aluminium nitride.
Give equation for the following conversion:Aluminium to sodium aluminate.
Give the chemical name and formula of ‘cryolite’.
4 tones of bauxite, 150 Kg of sodium hydroxide and 600 Kg of graphite.
The aluminium compound in bauxite is aluminium oxide and the main impurity is iron (II) oxide. Aluminium is obtained by the electrolysis of aluminium oxide dissolved in cryolite.
(a) When bauxite is treated with sodium hydroxide solution, what happens to:
(i) the aluminium oxide?
(ii) The iron (III) oxide?
- A to F below relate to the source and extraction of either zinc or aluminium:
- Bauxite
- Coke
- Cryolite
- Froth floatation
- Sodium hydroxide solution
- Zinc blende
- Write down the three letters each from the above list which are relevant to
- Zinc
- Aluminium
- Fill in the blanks using the most appropriate words from A to F.
- The ore from which aluminium is extracted must first be treated with ………………. so that pure aluminium oxide can be obtained.
- Pure aluminium oxide is dissolved in ….. to make a conducting solution.
iii. Write the formula of cryolite.
Name two metallic oxides which cannot be reduced by carbon, carbon monoxide or hydrogen.
