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प्रश्न
Give the principles of electromagnetic separation.
उत्तर
Magnetic properties of the ores.
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संबंधित प्रश्न
Describe with one example, how moderately reactive metals (which are in the middle of reactivity series) are extracted.
When an object made of metal A is kept in air for a considerable time, it loses its shine and becomes almost black due to the formation of a layer of substance B. When an object made of another metal C is kept in damp air for a considerable time, it gets covered with a green layer of substance D. Metal A is the best conductor of electricity whereas metal C is the next best conductor of electricity.
(a) What is metal A?
(b) What is metal C?
(c) Name the substance B.
(d) Name the substance D.
Answer the following questions based on the extraction of aluminium from alumina by Hall - Heroult’s Process :
Name the electrode, from which aluminium collected.
What is meant by concentration of ores?
How are metals refined by the electrolytic methods?
Answer the following question:
Carbon cannot reduce the oxides of sodium, magnesium, and aluminum to their respective metals. Why? Where are these metals placed in the reactivity series? How are these metals obtained from their ores? Take an example to explain the process of extraction along with chemical equations.
How is the method of extraction of metals high up in the reactivity series different from that for metals in the middle? Why can the same process not be applied for them? Name the process used for the extraction of these metals.
Write the molecular formulae of the following compound.
Cryolite
Explain in brief types of extraction of less reactive metals according to their reactivity.
2 mL each of concentrated HCl, HNO3 and a mixture of concentrated HCl and concentrated HNO3 in the ratio of 3 : 1 were taken in test tubes labelled as A, B and C. A small piece of metal was put in each test tube. No change occurred in test tubes A and B but the metal got dissolved in test tube C respectively. The metal could be
