Question

why do metals become dull on being kept open in air​

Answer 1

Answer:

Surface of some metals acquire dull appearance due to the process of corrosion. Corrosion is the process of slowly eating up of the metals due to attack of atmospheric gases such as oxygen, carbon dioxide, hydrogen sulphide, water vapour, etc. on the surface of the metals so to as to convert the metal into oxide ‘carbonate’ sulphide is known as corrosion. For example aluminium objects lose their lustre and become dull after sometime. This is due to the corrosion of aluminium. When aluminium is exposed to moist air its surface is covered with a thin impervious layer of aluminium oxide

Explanation:

Answer 2

Answer:

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