Question

explain why, the surface of some metals acquires a dull appearance when exposed to air for a long time.​

Answer 1

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Here is Your Answer...!!!

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↪Actually welcome to the concept of the Chemical Reactio of Oxidation ..

↪Such as here , some of the metals are reactive to nature that ,

↪after exporsure to air ,they come in contact with the oxygen and thus they react with the Oxygen from the air ..

↪Thus it forms a oxide layer on the surface of the metals and thus it appears as dull or dark

↪We can see this type of reaction in the followinh metals like

↪COPPER , ZINC , ALUMINIUM, IRON , SILVER

↪one of the such reaction is ..

↪Ag + O2 -----> Ag2O

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Answer 2

$<b>$Answer:-

The Surface of Some Metals acquires a dull appearance when exposed to air for a long time because It react with Oxygen present in the Atmosphere and form a thin layer of oxide on its Surface.

Metal + Oxygen ---------> Metal Oxide.

Few Metals are :-

Silver, Copper, Aluminium, etc.

Reaction which takes place are as Follows :-

♡ 2Ag + 02 ----------> 2Ag0.