Chapter 3: Metals and Non-metals

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Metals and Non-metals


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.


The copper vessels are tarnished due to the reaction of copper with moist air to form copper hydroxide and copper carbonate.

Cu + H2O + CO2 + O2 Cu(OH)3 + CuCO3

                  Moist Air                Green coating on copper

Lemon contains citric acid while tamarind juice contains tartaric acid. These acids dissolve the copper hydroxide and copper carbonate present on the tarnished copper and shiny red-brown appearance of copper occurs.

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