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प्रश्न
Observe the following diagram and write answers.
- Name the method.
- Write anode reaction and cathode reaction.
- Why fluorspar and cryolite are added in the mixture?
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उत्तर
- This method is electrolytic reduction of alumina.
- Anode reaction:
\[\ce{2O^{2-} -> O2 + 4e^-}\] (Oxidation)
Cathode reaction:
\[\ce{Al^{3+} + 3e^- -> Al_{(l)}}\] (Reduction) - Alumina has a very high melting point (>2000 °C). The purpose of mixing ‘cryolite’ and ‘fluorspar’ with ‘alumina’ in the electrolytic reduction of alumina is to carry out the process at a much lower temperature. Addition of cryolite and fluorspar reduces the melting point of alumina to about 1000 °C.
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संबंधित प्रश्न
Name the following:
The property possessed by metals by which they can be beaten into sheets.
Name one metal which is extracted by reduction with carbon.
Name the method by which aluminium metal is extracted.
Define the term ore.
Name one ore of copper (other than cuprite). Which compound of copper is present in this ore? Also, write its chemical formula.
Name two metals which are always found in combined state.
Some metallic oxides can be reduced by hydrogen, carbon and carbon monoxide and some cannot. Explain.
Give reasons, why aluminum is used in:
wrapping chocolates
Identify the process given in following passage and draw neat labelled diagram showing the process.
Electrolysis of molten mixture of alumina (melting point > 20000C) is done in a steel tank. The tank has a graphite lining on the inner side. This lining does the work of a cathode. A set of graphite rods dipped in the molten electrolyte works as anode. Cryolite (Na3AlF6) and fluorspar (CaF2) are added in the mixture to lower its melting point upto 10000C.
Answer the following questions based on the extraction of aluminium from alumina by Hall - Heroult’s Process :
What is the function of cryolite used along with alumina as the electrolyte?
Name the following:
Two metals which are found in the free or native state.
Name : The metal which is liquid at room temperature.
How many valence electrons are present in non- metals?
What is the difference between calcination and roasting?
_______ is the least reactive metal.
Sulphide ores : Roasting : : Carbonate ores : _______
In the electrolytic reduction of alumina, the lining of graphite acts as an anode.
Explain the following reaction with the balanced equation.
Zinc carbonate is heated strongly in limited supply of air
Explain in brief types of extraction of moderately reactive metals according to their reactivity.
The given reaction shows one of the processes to extract the metals like Iron and Manganese.
\[\ce{MnO2(s) + Al(s) -> Mn(l) + Al2O3(s) + Heat}\]
Identify the substance oxidised and reduced in the above reaction.
