When copper vessel is left in the atmosphere, it reacts with oxygen present in the atmosphere and forms copper oxide, which gives a dull appearance. It is alkaline in nature so when rubbed with lemon. The acid present in the lemon neutralizes the effect of base. And it begins to shine again?

When copper vessel is left in the atmosphere, it reacts with oxygen pr

1.	When copper vessel is left in the atmosphere, it reacts with oxygen present in the atmosphere and forms copper oxide, which gives a dull appearance. It is alkaline in nature so when rubbed with lemon. The acid present in the lemon neutralizes the effect of base. And it begins to shine again?
Answer» copper vessel is exposed to MOIST air for LONG TIME acquires a dull green colour which is form due to the formation of basic carbonate due to its reaction with CO2 Present in the air.