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प्रश्न
Which metal becomes black in the presence of hydrogen sulphide gas in air?
उत्तर
Silver metal becomes black in the presence of hydrogen sulphide gas in the air. Silver reacts with hydrogen sulphide gas in the air and forms a thin black layer of silver sulphide (Ag2S) on it. Therefore, silver jewellery or ornaments become dull due to the formation of silver sulphide coating on their surface.
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संबंधित प्रश्न
In the extraction of aluminium: Name the process of concentration of bauxite.
Give reasons.
Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
Name one metal which is extracted by reduction with carbon.
Name two ores of zinc. Write the names of the chemical compounds present in them and give their chemical formulae.
Give the chemical formula of :
Sodium aluminate
Answer the following questions based on the extraction of aluminium from alumina by Hall - Heroult’s Process :
Why is powdered coke sprinkled on top of the electrolyte?
Name the following:
The mixture of materials fed into a furnace to extract a metal.
Mercury, silver, gold are highly reactive metals.
Write the molecular formulae of the following compound.
Fluorspar
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.
