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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?
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.
APPEARS IN
संबंधित प्रश्न
Define the Ore.
Name two metals which are found in nature in the free state.
The process by which sulphide ore is concentrated.
In the extraction of aluminium: Write the function and formula of cryolite in the extraction of aluminium.
In the extraction of aluminium: Why is it necessary to replace anodes time to time?
How many carats is pure gold? Why is pure gold not suitable for making ornaments?
Why does a new aluminium vessel lose shine so soon after use?
Why do gold ornaments look new even after several years of use?
Name one metal which is extracted by reduction with carbon.
Fill in the following blank with suitable word:
Bronze is an alloy of copper and .........
Describe with one example, how moderately reactive metals (which are in the middle of reactivity series) are extracted.
State why aluminium is extracted from its oxide by electrolysis while copper, lead, iron by reducing agents and mercury and silver by thermal decomposition.
Give reasons, why aluminum is used in:
making alloys
Explain in brief types of extraction of moderately reactive metals according to their reactivity.
Observe the figure and answer the following.
- Write the name of the method.
- What is used as anode and cathode in this method?
- Write the molecular formula and use of cryolite.
- Write anode reaction.
- Write cathode reaction.
The process in which a carbonate ore is heated strongly in the absence of air to convert it into metal oxide is called ____________.
In thermite welding a mixture of ____________ is ignited with a burning magnesium ribbon which produces molten iron metal as a large amount of heat is evolved.
Electrical wires have a coating of an insulting material. The material, generally used is
On the basis of reactivity metals are grouped into three categories:
- Metals of low reactivity
- Metals of medium reactivity
- Metals of high reactivity
Therefore metals are extracted in pure form from their ores on the basis of their chemical properties.
Metals of high reactivity are extracted from their ores by electrolysis of the molten ore.
Metals of low reactivity are extracted from their sulphide ores, which are converted into their oxides. The oxides of these metals are reduced to metals by simple heating.
(a) Name the process of reduction used for a metal that gives vigorous reaction with air and water both.
(b) Carbon cannot be used as a reducing agent to obtain aluminium from its oxide? Why?
(c) Describe briefly the method to obtain mercury from cinnabar. Write the chemical equation for the reactions involved in the process.
OR
(c) Differentiate between roasting and calcination giving chemical equation for each.
The given reaction shows one of the processes to extract the metals like Iron and Manganese.
\[\ce{MnO2(s) + Al(s) -> Mn(l) + Al2O3(s) + Heat}\]
Give a reason why Aluminium is preferably used in thermite reactions.
