8. Give reasons for the following:
b) Iron cannot displace zinc from its solution.
c) A copper vessel acquires a dull green coating if exposed to
d) Silver jewellery turns dark over a period of time.
Answers
Answer:
Explanation
b) iron cannot displace zinc from its salt solution because zinc is more reactive than iron. More reactive metal displaces less reactive metal from its salt solution. Zn has displaced copper, but iron cannot do so.
c) Copper metal when exposed to air turns green in colour due to corrosion. When copper vessel is exposed to air in rainy season, the metal reacts with gases and moisture and atmospheric gases to form a mixture of copper carbonate and copper hydroxide. This gives a green colour to the surface of copper metal.
d) Silver becomes black because of hydrogen sulfide (sulfur), a substance that occurs in the air. When silver comes into contact with it, a chemical reaction takes place and a black layer is formed. ... Also sweat (which ammonia occurs in) raises the acidity of the skin and could tarnish the silver