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

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Q: (CDS-I/2020)
Silver articles become black after some time when exposed to air because

question_subject: 

Science

question_exam: 

CDS-I

stats: 

0,32,34,19,7,32,8

keywords: 

{'silver reacts': [0, 0, 0, 1], 'silver articles': [0, 0, 0, 1], 'silver oxide': [0, 0, 0, 1], 'silver carbonate': [0, 0, 0, 1], 'silver sulphide': [0, 0, 0, 1], 'silver': [0, 0, 0, 1], 'coating': [0, 0, 0, 2], 'nitrogen oxides': [0, 0, 0, 1], 'air': [1, 0, 0, 0], 'sulphur': [0, 0, 0, 2], 'moist carbon dioxide': [0, 0, 0, 1]}

The reason why silver articles become black over time when exposed to air is due to a chemical reaction that occurs between the silver and sulphur in the air, this reaction leads to the formation of silver sulphide which has a black appearance and forms a coating on the silver object, hence, option 3 is the correct answer. Let`s dissect the other options for better understanding:

Option 1: Silver does not typically oxidize to form silver oxide in normal conditions and even if it did, it would appear as a brown substance rather than black.

Option 2: Silver doesn`t easily react with carbon dioxide to form silver carbonate. If it did, the silver carbonate is a white substance, not black.

Option 4: Silver does not react with nitrogen oxides in the air under normal conditions. Even if it did, silver nitrate is a white crystalline substance, not a black coating.