Q28 of 400 Page 191

Why are the metals like Na, K, Ca and Mg never found in their free state in nature?

Na, K, Ca and Mg are very highly reactive metal and have their position among the reactive metals in the reactive series. This is the reason why, they cannot exist free in nature.

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26 Which property of 'solder' alloy makes it suitable for welding electrical wires? 27 Explain why, carbon cannot reduce oxides of sodium or magnesium. 29 Name one metal each which is extracted by:

(a) reduction with carbon.


(b) electrolytic reduction.


(c) reduction with aluminium


(d) reduction with heat alone.

 30 Fill in the following blanks with suitable words:

(a) The corrosion of iron is called ................


(b) ................ and ................ are necessary for the rusting of iron.


(c) The process of depositing a thin layer of zinc on iron articles is called................


(d) Tiffin boxes are electroplated with ................ but car bumpers are electroplated with ................ to protect them from rusting.


(e) The corrosion of copper produces a ................ coating of basic copper carbonate on its surface.


(f) Brass is an alloy of copper and ..............


(g) Bronze is an alloy of copper and ..............


(h) The non-metal present in steel is ..............


(i) The alloy in which one of the metals is mercury is called an.............


(j) The electrical conductivity and melting point of an alloy is .............. than that of pure metals.


(k) The rocky material found with ores is called..............