Explain the following terms with one example each.
(a) Corrosion
(b) Rancidity
(a) Corrosion: Metal are reacted with atmosphere oxygen, carbon dioxide and moisture and converted into metal oxides and carbonate. This phenomenon is called corrosion.
Eg.:
(i) Black coating on silver.
4Ag + 2H2S + O2 -----------> 2Ag2S + 2H2O
(ii) Green coating on copper.
Cu + CO2 + H2O -----------> CuCO3. Cu (OH)2
(b) Rancidity: Oil and fat containing items when comes in contact with atmosphere oxygen they get oxidised and start smelling and tasting bad. The food item have gone rancid. This phenomeon is called rancidity.
Eg.:
(i) Smell and taste on food items get change after some times.
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