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.


(e) What type of chemical can be used to remove the green layer from metal C and clean it? Why?

(a) Metal A is silver. Because when silver is kept in air for a considerable time, it loses its shine and becomes almost black due to the formation of a layer of silver sulphide.

(b) The name of the metal C is copper.


(c) The name of the substance is silver sulphide.


(d) The name of the substance D is basic copper carbonate.


(e) Dilute acidic solution can be used to remove the green layer from metal C and clean it because the acid solution dissolves green coloured basic copper carbonate present on the corroded copper object makes it look shiny, red brown again.


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