Question

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.

Answer 1

Hint: Lemon reacts with the basic copper oxide and a salt is formed. This salt is removed by washing the copper vessel with water. Thus removing the base and making the vessel to shine.
By using the above information, try to explain why these sour substances are effective in cleaning.

Complete step by step answer:
So, basically copper vessels generally get tarnished (change color) when kept in open. It is due to the formation of a black layer of copper oxide and a green layer of copper carbonate on the copper vessel when it comes in contact with the light and oxygen.
These copper oxide and copper carbonate are basic in nature. Lemon is generally acidic in nature. So it is used to rub the copper vessels. Lemon reacts with the basic copper oxide and copper carbonate to form a salt. This salt is removed by washing the copper vessel with water. Thus removing the base and making the vessel to shine.

Therefore, copper can change color when it encounters carbon dioxide. The tartaric acid contained in tamarind removes the color coat and makes copper get back to its original color.

Note: We can prevent the oxidation of copper by using some kind of grease, such as a layer of Vaseline, over the copper so that we can prevent copper corrosion.