Question

a) A student has been collecting silver coins and copper coins. After some days,
when she took out the coins to count, she observed a black coating on silver
coins and green coating on copper coins. Which chemical phenomenon is
responsible for such coatings? Write the chemical reactions involved.
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Answer 1

HELLO DEAR,

when silver react with hydrogen sulphide in presence of air (oxygen)

to form a silver sulphide in black colour

Equation is :-

2Ag + H2S ---------- Ag2S +H2

copper metal is naked to moist air(oxygen)

due to

formation of copper carbonate ( corrosion of copper) it develops a green layer

Equation is:-

2Cu + O2 + CO2 + H2O → CuCO3.Cu(OH)2

I HOPE ITS HELP YOU DEAR,

Answer 2

Answer:

because when an metal is reacted with air and oxygen so it gives rise to a a layer and this process is known as corroding of metal or corrosion.

ag+3/2 O2+×H2O➡️ag2o3.xH2O