Chemistry
Explain with reasons:
In the electrolytic reduction of alumina, the graphite anode is gradually consumed.
or
Why the anode has to be replaced from time to time in this process?
Metallurgy
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Answer
In the electrolytic reduction of alumina, the graphite (anode) is oxidized by oxygen to CO and further forms CO2, so it is consumed and has to be replaced from time to time.
Equation:
2C + O2 ⟶ 2CO
2CO + O2 ⟶ 2CO2
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Related Questions
Aluminium is extracted from it's chief ore, bauxite. The ore is first purified and then the metal is extracted from it by electrolytic reduction.
(a) Write three balanced equations for the purification of bauxite.
(b) Name a chemical used for dissolving aluminium oxide. In which state is the chemical used?
(c) Write an equation for the reaction which takes place at the anode during the extraction of aluminium by the electrolytic process.
(a) A to F below relate to the source and extraction of either zinc or aluminium:
A. Bauxite
B. Coke
C. Cryolite
D. Froth floatation
E. Sodium hydroxide solution
F. Zinc blende
(i) Write down the three letters each from the above list which are relevant to
- Zinc
- Aluminium
(ii) 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.
Explain with reasons:
Roasting is carried out on sulphide ores and not on carbonates ores.
Explain with reasons:
Carbon can reduce lead oxide but not aluminium oxide.