Question

Give reasons for the following: a) Silver and copper lose their shine when they are exposed to air. Name the substance formed on their surface in each case. b) Tarnished copper vessels are cleaned with tamarind juice. c) Aluminium is more reactive than iron yet there is less corrosion of aluminium as compared to iron when both are exposed to air.

Answer 1

A) Silver and copper undergoes corrosion which results in formation of silver. sulphide as silver reacts with atmospheric hydrogen sulphide and copper forms basic copper carbonate when reacts with atmospheric gases.
B)Tarnished copper vessels have deposits of basic copper carbonate which is basic in nature.Therefore when tamarind juice which is acidic in nature neutralise the salt
C)When aluminium corrodes it forms a non reactive layer of aluminium oxide which prevents further oxidation.

Answer 2

1:
Ag reacts with sulphide and form Ag2S
&CuCo3
2:
this is basic and tarmarind contains acid it neutrolises