Solutions of Metals and Non-metals (Page No - 196) - Chemistry Lakhmir Singh, Class 10 | Extra Documents, Videos & Tests for Class 10 PDF Download

Question 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. Mention the physical sates 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.
Solution :
(a) A is iron ( III ) oxide and B is aluminium powder.
(b) C is molten iron metal and D is aluminium oxide.

(c)
(d) This reaction is called thermite reaction. It is used for welding of broken pieces of heavy iron objects like railway tracks, etc.
(e) Displacement reactions and oxidation-reduction reactions.

Question 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 ?
Solution :
(a) Positively charged carbon electrode (Anode)
(b) This carbon electrode is burnt away because oxygen produced during the electrolysis of molten aluminium oxide reacts gradually with the carbon of carbon anode to form carbon dioxide gas.

Question 96:
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.
Solution :
(a) X is aluminium and Y is zinc.
(b) X is more reactiv e than Y.
(c) Bauxite; Al₂ O₃ .2H₂O
(d) Calamine, ZnCO₃
(e) Alloy of metal X : Duralumin ; Allo y of metal Y : Brass

Question 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.
What type of chemical can be used to remove the green layer from metal C and clean it ? Why ?
Solution :
(a) Silver
(b) Copper
(c) Silver sulphide
(d) Basic copper carbonate
(e) Dilute acid solution; The acid sol ution dissolves green coloured basic copper carbonate present on the corroded copper object makes it look shiny, red brown again.

Question 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 ?
Solution :
Metal P is zinc; Metal Q is tin; Metal R is lead; Metal S is iron.
Metal P (zinc) is used to form a thin layer on metal S (iron) by the process of galvanisation to prevent its corrosion.
Metal Q (tin) i s used for electroplating tiffin boxes made of metal S (iron).
Metal R (lead) is used in making car batteries.
Metals Q (tin) and R (lead) form an alloy called solder .

Question 99:
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.
Solution :
(a) Manganese
(b) Manganese dioxide
(c) Aluminium
(d) Chromium

Question 100:
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.
Solution :
Metal X is gold and Metal Y is silver; The colour of metal X (gold) is yellow.