Silver articles become black after some time when exposed to air

Silver articles become black after some time when exposed to air because

[amp_mcq option1=”silver gets oxidized to silver oxide” option2=”silver reacts with moist carbon dioxide in the air to form silver carbonate” option3=”silver reacts with sulphur in the air to form a coating of silver sulphide” option4=”silver reacts with nitrogen oxides in the air to form silver nitrate” correct=”option3″]

This question was previously asked in

UPSC CDS-1 – 2020

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Silver articles tarnish and become black when exposed to air primarily due to a reaction with small amounts of sulfur compounds (like hydrogen sulfide, H₂S) present in the atmosphere. This reaction forms a thin layer of silver sulfide (Ag₂S) on the surface, which is black.

– Silver reacts with sulfur compounds in the air.
– The reaction produces silver sulfide (Ag₂S).
– Silver sulfide is black, causing the tarnish.

While silver can react with oxygen at high temperatures to form silver oxide, the black tarnish at room temperature is predominantly due to the formation of silver sulfide. Sources of hydrogen sulfide in the air include pollution, volcanic activity, and the decomposition of organic matter.

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