Question

dull surface of copper starts shining when we rub it with a lemon why

Answer 1

dull surface of copper is basic in nature I.e. CuCo3(OH)2 and lemon contain acid that is citric acid so when we rub lemon on copper vessel then acid react with base and become neutral so copper start shinning

Answer 2

Because a green layer of copper carbonate get formed on copper on rubbing it with lemon which is acidic Inn nature this, layer get vanished