Q13 of 31 Page 56

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.

Tarnished copper vessels are cleaned with lemon or tamarind juice as the acids contained in them dissolves the coating of copper oxide or basic copper carbonate present on the surface of the vessels and makes them shining red-brown again.


More from this chapter

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11

What type of oxides are formed when non-metals combine with oxygen?

 12

Give reasons:

(a) Platinum, gold and silver are used to make jewellery


(b) Sodium, potassium and lithium are stored under oil.


(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.


(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.

 14

Differentiate between metals and non-metals on the basis of their chemical properties.

 15

A man went from door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used ?