Lakhmir Singh and Manjit Kaur Solutions for Chapter: Metals And Non-Metals, Exercise 14: Questions Based on High Order Thinking Skills (HOTS)

A metal which exists as a liquid at room temperature is obtained by heating its sulphide ore in the presence of air. 
(a) Name the metal and write its chemical symbol.
(b) Write the name and formula of the sulphide ore. 
(c) Give the equations of chemical reactions involved in the production of metal from its sulphide ore. 
(d) Name a common device in which this metal is used. 
(e) Can this metal displace copper from copper sulphate solution? Why ?
 

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. 
Mention the physical states of all the reactants and products in this equation and indicate the heat change which takes place. 
(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.
 

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?
 

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 of 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.
 

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?
 

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?

A black metal oxide XO₂ is used as a catalyst in the preparation of oxygen gas from potassium chlorate. The oxide XO₂ is also used in ordinary dry cells. The metal oxide XO₂ cannot be reduced satisfactorily with carbon to form metal X. 
(a) Name the metal X. 
(b) Name the metal oxide XO₂ 
(c) Which reducing agent can be used to reduce XO₂ to obtain metal X ? 
(d) Name another metal which can also be extracted by the reduction of its oxide with the above reducing agent. 
 

Metals X and Y can be recovered from the anode mud left behind after the electrolytic refining of copper metal. The coins made of metal X look new even after several years of use but the coins made of metal Y lose their shine gradually and get blackened soon. When metal X is alloyed with a small amount of metal Y, it becomes hard and hence suitable for making ornaments. What are metals X and Y? Also state the colour of metal X.