You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.

Explanation

When copper vessels are exposed to moist air, they form a green coating of basic copper carbonate `[CuCO_3.Cu(OH)_2]`
`2Cu+underbrace(CO_3+O_2+H_2O)_((f rom moist air))toCuCO_3.Cu(OH)2_(Basic copper carbonate (Green))`
The sour substances such as lemon or tamarind juice contain acids. Lemon juice contains citric acid and tamarind contains tartaric acid. These acids dissolve the coating of copper oxide or basic copper carbonate, present on the surface of tarnished copper vessels and make them shining red brown again.