Q96 of 400 Page 195

A metal X which is resistant to corrosion is produced by the electrolysis of its molten oxide whereas another metal Y which is also resistant to corrosion is produced by the reduction of its oxide with carbon. Metal X can be used in powder form in thermite welding whereas metal Y is used in making cathodes of ordinary dry cells.

(a) Name the metals X and Y.


(b) Which of the two metals is more reactive: X or Y?


(c) Name one ore or metal X. Also write its chemical formula.


(d) Name one ore of metal Y. Also write its chemical formula.


(e) Name one alloy of metal X and one alloy of metal Y.

(a) X is aluminium and Y is zinc, this can be determined by the above given statement.

(b) Among the two metals X and Y, X is more reactive then that of the Y.


(c) the name of the ore is Bauxite and its chemical formula is Al2O3.2H2O.


(d) The name of the ore of metal Y is Calamine and its chemical formula is ZnCO3.


(e) The name of the alloy of metal X is Duralumin and the name of the alloy of metal Y is Brass.



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94 No chemical reaction takes place when granules of a rusty-brown solid A are mixed with the powder of another solid B. However, when the mixture is heated, a reaction takes place between its components. One of the products C is a metal and settles down in the molten state while the other product D floats over it. It was observed that the reaction is highly exothermic.

(a) What could the solids A and B be?


(b) What are the products C and D most likely to be?


(c) Write the chemical equation for the reaction between A and B leading to the formation of C and D.


(d) What is the special name of such a reaction? State one use of such a reaction.


(e) Name any two types of chemical reactions under which the above reaction can be classified.

 95 In an electrolytic tank, aluminium metal is being extracted by the electrolysis of molten aluminium oxide using carbon electrodes. It is observed that one of the carbon electrodes is gradually burnt away and has to be replaced.

(a) Which carbon electrode (cathode or anode) is burnt away?


(b) Why is this carbon electrode burnt away?

 97 When an object made of metal A is kept in air for a considerable time, it loses its shine and becomes almost black due to the formation of a layer of substance B. When an object made of another metal C is kept in damp air for a considerable time, it gets covered with a green layer of substance D. Metal A is the best conductor of electricity whereas metal C is the next best conductor of electricity.

(a) What is metal A?


(b) What is metal C?


(c) Name the substance B.


(d) Name the substance D.


(e) What type of chemical can be used to remove the green layer from metal C and clean it? Why?

 98 Four metals P, Q R and S are all obtained by the reduction of their oxides with carbon. Metal P is used to form a thin layer over the sheets of metal S to prevent its corrosion. Metal Q is used for electroplating tiffin boxes made of metal S whereas metal R is used in making car batteries. Metals Q and R form an alloy called solder. What are metals P, Q R and S? How have you arrived at this conclusion?